What version of Premiere Elements and on what computer operating system is it running?
The Adobe watermark appears in the trial version in the Edit area monitor. It will remain there until you purchase the program.
Any exports from the tryout (burn to disc or export to file) have the watermark which cannot be removed even after purchase.
But you can remove the Adobe watermark from the tryout project file after purchase of the product...
a. open the tryout project in the tryout, go to Timeline Menu/Delete Rendered Files...the Adobe watermark should be gone from that project file
b. open the tryout project in purchase product and do nothing...the Adobe watermark disappears.
"a:" is the classical solution and "b" has worked for many of us.
I have not run into the issue that you have described. Consequently, please give more details...
a. Is this event happening only when you open a tryout project file?
b. Is this event happening even if you open a new project in the purchased product?
Once I have more information, we might consider
a. deletion Adobe Premiere Elements Prefs file (flushing the preferences)
b. uninstall, free ccleaner run through (regular and registry cleaner parts), reinstall with antivirus and firewall(s) disabled.
Is the Cross Dissolve video transition the only one involved in this event?
You mention Product Key...what about a purchased serial number. Have you gotten that yet? Nonetheless, it is not yet clear to me why the issue is singling out Cross Dissolve video transition.
Please review and consider, supply more details, and we can then decide what next.