Hi Mark
thank you for responding. I am not that tech savvy, but with some help from google, I think I have found the error
Uncaught RangeError: Maximum call stack size exceeded
So does this mean that I have blocked too many IP's.
Although sdayman mentions that deactivating Wordfence may solve the problem, I do in fact have IP's who have tried continually (250 times for example) of trying to log in 3 months or so after I have blocked them. Now that I can't see the blocked IP's, I can't see who the culprits are anymore. When I try to block spammers, it is not working, as I can't seem to block IP's or if I have I can't see whether it has happened or not.
thanks for responding. :)