Following Problem

OK Blippers, I do not contribute here much, but have a question that someone may have the answer to.

Someone want to follow me, but is being prevented:-

"My journal is private but you can request to follow me and I will say yes. Yours just says forbidden to follow?????"

Seems weird to me. I have checked all of my settings etc. etc. and can find nothing that may give rise to this problem. So, I tirn to the hive mind in the hope of a solution.