There have been loads of articles floating around the Internet in the last couple of weeks, on how to work from home, and how to manage remote teams and so on. Not only are your staff adjusting to WFH, but you're adjusting to managing remote workers, and if you've not done it before, there are some challenges which aren't relevant when you're all in the office.
Have you provided laptops for people to WFH, with a standard build, so you know people have the right applications? Or are you expecting people to provide their own?
You need to look at the tools available to you - collaboration software, whether it's MS Teams, Google Hangouts, Zoom, Skype, loads of others. Make sure everyone can connect. Have meetings. Make sure everyone is there. This will be harder to enforce if they are providing their own hardware.
You really need to focus on the processes (and data protection) - how it worked with everyone in the office isn't working now some people are WFH, and you need to change things so they can work, for the business as well as everyone working there - you can't afford to let people get too pissed off about things as it affects morale, but it sounds like they are not unreasonable to be feeling fed up.
It is down to you to manage it all, but that doesn’t mean you're on your own - get input from your staff about how they think processes could be improved. Your optical project isn't complete, but there's bound to be other things you can do, dividing work up differently, and so on.