This is imho the worst part of WFH. Some people come to work at 6:00 and go home at 14:00, some come at 10:00 and leave at 18:00, and some even later. If you're in an office, the latecomer can just check the early birds office, "oh, you're here, can we ..." / "he's not here anymore, this will wait 'till tomorrow". With WFH it's constant emails and work calls, and for a lot of people it's hard to separate work/home, turn the work phone off (especially in small companies, where before the plague, if someone called you in the afternoon, it usually meant something horrible has happened).
The second thing i'd miss is all the non-work activities that happen at work, from random chatter, to lunch, practical jokes, etc. Also when dealing with clients, the after-meeting-beer usually solved a lot of problems with a lot of one-on-one chats, and informal talks about rwhat the issues are,... this is hard to do on zoom/teams/..., especially if there is a higher-up present, and the engineers are afraid to honestly say what's bothering them during day-to-day work.