What is it that I can do to be more likeable?

There is no need to people to like you (unless you care about that): you want people to respect you as a professional and in general are happy working with you. So you I recommend start working on your professional skills and leave the personal stuff aside.

Step number 1 would be your communication skills. A little emphasis and preparation goes a long way here, especially if you deal with people at the director and/or exec level.

Try to see the world from there perspective. While your workshop feels very important to you, it's probably just another "to do" item on their long list. They get requests like this all day long and expecting them to remember interactions with you in great detail is unrealistic.

There are things that you can do to communicate more effectively:

1. Do a little bit of homework up front: who is this person, what do they do, and how important or annoying is your request to them.
2. Check whether you can figure their most preferred communication style: message, Google Drive, call, short and to the point vs. fluffy and flowery, etc. Everyone is different, so adapting to someone's preferred style makes things a lot easier.
3. Organize your information well and make it easy to find and look up. E-mail chain are the "dumpster" of corporate communications: no one wants to rummage around in there.
4. Learn the "state of the art". Talk to your boss about communication culture in your company: what style, what tools, what tone of voice is considered "normal". Often HR has guidelines and classes around this.

It did not seem to me that my manager tried to defend me as he did not even do his research to see that i had replied and read the other conversations going on.

What exactly do you want your manager to defend. You DID honk off two execs enough for them to complain. The complaint is NOT about the accuracy or factual content, it's about efficiency/appropriateness. Both are very important.

it is already attached and here is your time slot. I also request everyone to join 5-7 mins prior for ease"

And what makes you think that your workshop is more important than anything else an exec has to do, so that you can demand 5-7 minutes extra time. Wouldn't it be better for the company if the exec uses that time to recalibrate a project that's off the rails, talk to a difficult employee, or close a deal with an important customer?

An alternative response could have been "Happy the help: you're on from 3pm to 4pm. I can poke an invite in your calendar and I'll attach a link to a shared doc that has goals, agenda, the detailed schedule, and a presentation template, if you want one. Does that work for you?"

... 40-50+ year old men who are tenured in the industry. I am a female in my 20s ...

That has nothing to do it with. Effective communication is important between all levels, roles and genders. This is not about hierarchy, it's about viewing the world from the other person's perspective and not just use your own point of view. Putting some effort into learning the tools of the trade will serve your career very well.

What is it that I can do to be more likeable?

There is no need for people to personally like you (unless you care about that): you want people to respect you as a professional and to be happy working with you. So you I recommend start working on your professional skills and leave the personal stuff aside.

Step number 1 would be your communication skills. A little empathy and preparation goes a long way here, especially if you deal with people at the director and/or exec level (but this applies to everyone you talk to).

Try to see the world from there perspective: While your workshop feels very important to you, it's probably just another "to do" item on their long list. They get requests like this all day long and expecting them to remember interactions with you in great detail is unrealistic.

There are things that you can do to communicate more effectively:

1. Do a little bit of homework up front: who is this person, what do they do, and how important or annoying is your request to them and how does fit into their goals. Can you create some synergy or overlap?
2. See whether you can figure their most preferred communication style: message, calendar, Google Drive, call, short and to the point vs. fluffy and flowery, etc. Everyone is different, so adapting to someone's preferred style makes things a lot easier and smoother.
3. Organize your information well and make it easy to find and look up. E-mail chains are the "dumpster" of corporate communications: no one wants to rummage around in there.
4. Learn the "state of the art". Talk to your boss about communication culture in your company: what style, what tools, what tone of voice is considered "normal". Often HR has guidelines and classes around this.

It did not seem to me that my manager tried to defend me as he did not even do his research to see that i had replied and read the other conversations going on.

What exactly do you want your manager to defend? You DID honk off two execs enough for them to complain. The complaint is NOT about the accuracy or factual content, it's about efficiency/appropriateness. Both are very important.

it is already attached and here is your time slot. I also request everyone to join 5-7 mins prior for ease"

And what makes you think that your workshop is more important than anything else an exec has to do, so that you can demand 5-7 minutes extra time. Wouldn't it be better for the company if the exec uses that time to recalibrate a project that's off the rails, talk to a difficult employee, or close a deal with an important customer?

An alternative response could have been "Sure: you're on from 3pm to 4pm. I can poke an invite in your calendar and I'll attach a link to a shared doc that has goals, agenda, the detailed schedule, and a presentation template, if you want one. Does that work for you? Anything else I can help with?"

... 40-50+ year old men who are tenured in the industry. I am a female in my 20s ...

That has nothing to do it with. Effective communication is important between all levels, roles and genders. This is not about hierarchy, it's about viewing the world from the other person's perspective and not just use your own point of view. Putting some effort into learning the tools of the trade will serve your career very well.