My dog got used to me working from home, how do I fix that now?

A dog that has spent months with constant company has effectively unlearned whatever alone time tolerance it had before, so the fix is the same structured, gradual process used with any dog new to being left, not a shortcut because the dog has technically done it before.

Practice leaving the house for genuine short errands, or even just sitting in the car in the driveway for 10 minutes, to give the dog real, low stakes practice with actual departures rather than only in home separation.

If you know when full time office days will resume, work backward from that date, aiming to reach a comfortable 4 to 6 hour session at least a week before it becomes necessary, rather than testing it for the first time on an actual full return to work day.

Noting the date and length of each practice session, along with how the dog seemed on camera, gives a clear, honest picture of whether the plan is on track or needs to slow down, which is far more reliable than a general impression formed after a busy week. This record also becomes genuinely useful if a behaviorist ever needs to be brought in, since it shows exactly what has already been tried and how the dog responded at each stage of the process. Even a few lines jotted down after each session, rather than a formal spreadsheet, is enough to reveal a meaningful pattern over a couple of weeks.