Your Eating Schedule Changes
You likely had your breakfast before going to work, and then eating lunch at work, and then eating dinner at home before going into quarantine. You probably had a snack after in the evening. However, now that you are in quarantine, you may be skipping breakfast, or eating a late one, and having a few snacks in between lunch and dinner. And having more snacks.
That is going to disrupt your system and cause weight gain. As hard as it is, it is important to stick to the regular eating schedule that you had before the quarantine. It will end at some point.