Not enough information to be of much help, unfortunately. You don't mention what kind of SSL certificates you're using, whether they are properly configured, and what device(s) and OS version(s) you're testing with.
My guess is that you've either got a self-signed certificate in place (don't bother with that), OR the SSL certificate isn't correctly configured. I've seen a lot of times where the intermediate CA is missing in the chain, and this can often cause validation to fail. Double check your configuration (I like SSL Server Test (Powered by Qualys SSL Labs) ) and fix any errors that are identified.