I would understand that my only option is to use the non-secure port if this had never worked, but it was working perfectly until a few weeks ago. I just tested from another computer and got the same results: RP connects secure with no trouble but M1ToGo gives this SSL error.
To me this indicates that there is some problem with the M1XEP. Is there some way to reset the XEP to factory defaults and then re-configure it to see if that helps?
Alternatively, is there any way to get more insight into the exact error code (the “-3” of “Secure SSL negotiation failed, code: -3”)?