I just experienced my first licence problem with MC26 as well. I think I may have been running 26.0.14 or slightly later, clicked on Help>Update Channels>Check For Updates like I normally do once a fortnight, and was told that Media Center is updating. However after I clicked on the Restart button, when Media Center restarted I was told I was running a 30-day trial version. I think the version it updated to was 26.0.18. I visited this forum to see if anybody else was having problems, and noticed that the latest version was 26.0.19 (which it couldn't update to automatically), so I manually downloaded this most recent version and installed it.
Installing 26.0.19 didn't help - it still showed the 30-day trial version. So I entered in my MC26 Registration Code and it was fine. However I then received an email saying "You have just restored a license for JRiver Media Center. There are 10 restores available in each 12 month period. There are 9 restores remaining at this time" etc etc.
Now this isn't a major issue because I can't see myself using 9 restores over the next 12 months (provided it updates normally). However it WILL become a major issue if this occurs every time Media Center is updated (like it would be for Dap who has had this problem the last three updates).
Thank you for your help, if you need any more information let me know. Hopefully this issue can be replicated and investigated.