I'm a manager at a consulting firm and 3 out of 5 people have left the team because they are 'fed up' with work from home. They say theres no boundaries between professional and personal work and they dont get office perks anymore like gyms, free coffees, networking. Anyone have any bright ideas on how to retain staff?
This depends very much on what your locale is and what your competitors are doing. If you are in a region where work-from-home (WFH) is not mandatory but you are making it mandatory for your employees, then perhaps you should stop doing that and allow them to go to the office if they like. If you're the only one making them work from home and other companies aren't, then they'll find a company that isn't and leave yours. However, if all companies are doing WFH now, then they might not find greener pastures.
Failing that, consider the demands you are placing on them; if you are calling them at 7pm to do work "because they can", stop doing that. Your people should only work 9-5 (or 10-6, or whatever your standard hours are), even if they can work 24h if they have to because they work from home. This goes for your clients as well: your clients should not be expecting your people to work outside of work hours, and if they are then it's your job as the manager to fix that by discussing the matter with your clients.
It's also possible that your people aren't being asked to work outside of normal hours, but there is the perception that they are expected to and so they do. You need to fix this perception issue by explicitly telling them "I know you work from home, but you are only expected to be online from 9am to 5pm and otherwise you can feel free to ignore whatever you are asked to do until the next business day".
Another way to solve the above problem would be to provide them with "work computers" (if you don't already). Here's a situation: You work from your home computer, so the same computer you use for work during the day is also the same computer you use for unwinding and gaming at night. So you're in the middle of your game of League of Legends or Fortnite or whatever (I don't PC game so I don't know what the new hotness is these days) and suddenly you receive a work message over IM. Some people (myself included) are good at just making a mental note of the message and replying in the morning. Other people feel the need to respond to that message immediately, even though it's out of work hours, and so they feel that they are unable to separate work and life. This sounds like an "it's their problem not mine" issue, but some people don't work like that, they can't solve their own problem. The best way for you to solve it is to give them a "work laptop" that they use at home, and when 5pm rolls around, you can just close it, throw it in your desk drawer, and not worry about it until the next day. It helps to retain the barrier between work and life.
As for the other perks, maybe you can think of something else to compensate them instead? Like if they used to get free coffee, then instead let them expense 1 Starbucks trip per day to the company, or if they had a gym membership then, I dunno, give them a pay raise by like $50 or whatever a monthly gym membership would cost?