I saw that someone else had a similar issue, but I am submitting a new question because I have done all of the things suggested for them without success.
For starters, this problem started over a month ago. I have been working with my developers in India about the problem (they are now unresponsive), and I have worked with my Siteground Live Chat and advanced support.
I have renamed the plugins folder and tried activating each plugin one at a time to isolate the one causing the problem with mixed results. Once I thought I knew the culprit, then I would have the same problem again. Then, if I was able to log in at all, once I tried to access the network, I'd be logged out again. Hosting company has no more suggestions.
Was able to log in last week after developers deactivated the Captcha plugin, but now I can't log in again. Is there anyone that can resolve this for me? I am not familiar with code at all and have far surpassed the limit of my knowledge.