Your first goal should be to reproduce the problem - because you can't know what to fix if you don't know what it is, and if you can't reproduce the problem then how will you know if your fix is working?
1. Gather more information. What SSL error? Surely there's some more specific information someone can give you? Like an actual error message, maybe?
2. Apply some logic. Which users are seeing this? What do they have in common? Do they have anything in common at all? Can the users successfully log in at another time?
3. Think about it from a technical standpoint. There are tons of possible SSL errors (see action item 1) but most of them boil down to the server not giving an appropriate cert. Do you have multiple servers? Is there a load balancer? Geographic CDNs? Are you sure they're all configured with identical information and up-to-date certificates?
4. Examine the details. "Certain static content not found" isn't any error message I've ever seen before - assuming it's a literal message. Where is it coming from? Under what conditions will it be emitted?