Having just installed Lightroom 6 from a CD none of my files (catalog, irat) transferred over from Lightroom 5. Nor did the popup appear asking whether I wished to change the previous catalog from 5 to 6. When I used the trial version there was no problem.
The conversion took place when you installed the trial version. Your catalogs were upgraded then. Isn't necessary to upgrade them again when installing Lightroom 6 because LR 6 and CC both use the same catalog format.
OK but when I open LR6.1 the catalog list "all photographs" shows 0.
Two things to try:
Go to File->Open Recent and see if the last catalog you were using is listed and click on it if it is.
With Lightroom closed, go to the folder containing your catalog and double-click on the catalog you were using with the trial version.