Appeal to solidarity?

The thing I can think of is "Flag waving" which uses appeal to emotion to manipulate a group.

In this instance, the implication is that the those working in the stores require solidarity and therefore to not satisfy that need is to let down those workers. 

Flag waving also incorporates an ad populum sentiment that we must all act as one in action and deed and therefore it is the right thing to do.

I don't see a fallacy.

I can see reasons to disagree and fallacy is not the only basis.

Team-building ("solidarity"), especially if it's recognized and appreciated by the store employees, may be a goal of the head office.

OTOH, if it's not valuable to the store folks, it could be just virtue-signalling Tokenism .

Without knowing the history of the head office, I don't see a fallacy.

If I understand this correctly, it is basically

If group X suffers, we should suffer as well to show our solidarity.

This concept or idea can be debated, but I see the main problem in the trade off . Take for example one plant that goes on strike. Another plant may do the same to show solidarity (i.e., they are striking for the rights/benefits of the other plant, not their own). They might sacrifice risking their jobs, not being paid, etc., which, arguably, is a reasonable trade off. In your case, the sacrifice for solidarity is the unnecessary risk of death, serious illness, and spreading the virus. I would argue that this is unreasonable, that is, the risk of death, serious illness, and spreading the virus far exceeds the benefits of "solidarity," I would think any reasonable employee that can't work from home would agree.

* Just a note that at some point, the risk of death, serious illness, or spreading the virus will become negligible so that this idea of "solidarity" becomes reasonable.