I notice this happening for a while, if I go to Manage Sites and then click on a website that shows plugin updates (this is the URL):
If I then have it update a plugin, MainWP shows the Confirmation Modal which I click Yes on and then nothing happens except the Modal closes. It doesn’t matter what website I choose.
I can update website plugins on other pages in MainWP like going from the Overview and then clicking “See Details” from the Plugin Updates line:
which is how I usually do it.
I have several MainWP extensions installed including WPvivid for backups so I am not sure if it is MainWP with a bug or if it is some how an extension.