Generally that should not happen.
The catalog issue was happened with me one time when my catalog was placed on an external hard drive and it was not plugged in when I opened my new Lightroom.
So it created a new catalog.
Also have you changed the location of preferences in the prior version ?
After the upgrade, I opened Lightroom and I think it was a fresh copy since it did not open my current catalogue but opened a new one. My current catalogue is probably not in the default location but is located in "C:\Lightroom Catalogue Folders". I realised straight away that my files were missing and loaded in my current catalogue. However some of my preference settings were lost. My "Preferences" file is in the default location for Lightroom CC and has never been moved.
As catalog was not on default location, eventually that should not make any difference, lightroom should open the last opened catalog.
So are you able to set the preferences for new Lightroom ?
When upgrading the LR installer builds a new Preferences file using the current Preferences file information. Depending on the how old the previous version is (3 to 6) the new Preferences file doesn't always work properly as you've discovered. I suggest resetting your current Preferences file to insure proper operation. You'll need to manually restore your Preferences settings and reload any LR plugins.
Yes I have reset them. I have everything working correctly now. Just wanted to establish what procedure I should follow at the next upgrade. Thanks for your replies.
Thanks for your reply. Everything is now reset correctly and i will be more aware of the issues at the next upgrade.