Elements 15 requires sign in

I purchased Adobe Elements 15 about two years ago and have been successfully using the program until today.  The software requires that I sign in and either enter the licensing serial number or use the program for a 30 day trial.  Unfortunately, I do not have the serial number readily available to me and require the program for a current project.  Can I use the 30 day trial and when I can obtain the serial number of the software I have already purchased, license the software again?  A secondary question is why Adobe has locked me out of my purchased program?  I tried contacting Adobe Support through chat but was disconnected twice today.