I am fairly new here, so my problem may not have the same cause as yours.

When I started, I had a lot of people following me immediatly and I just decided to also follow them in one fell swoop, clicking through them all. Looking at it a bit later, I notice that a lot of the people I wanted to follow were actually not followed by me, so I did it again at a later time.

When I did that, I noticed that some kind of error message kept popping up in the left bottom corner. My hunch is that I followed these persons a bit too quickly for the server to keep up, so I have to do it a bit slower.