1) Working out of my bedroom. I think a lot of people forget that some people simply don't have the living space to make a home office or can't go out (accessibility issues) in a way that a proper office allowed. By far the hardest psychological part of Covid to deal with; I have a lot more empathy for prisoners in solitary confinement now. Going out once a month is not what the body/mind was meant to have.
2) Not having the work social circle and chatter. I consider myself an introvert but I still find myself missing the short conversations in the open office and in the hallways that often led to new ideas implemented, quick checkups, social integrity.
3) Not having work equipment. I'm a designer. Been able to work off of the laptop fairly well, but I miss our (specialized) printers deeply.