At the Launcher and Install tab under settings click on Change Trainz update stream...
A window will come up displaying the current path it finds with Change Targets...
Here's the "important" part. Make sure this path is pointing to your TRS22 PE installation and not your TRS-PLUS installation. If you have to, you can click on Change Targets... and browse in the Explorer-like window for your TRS22 PE installation.
Once you find it, click Next...
Login to your My Trainz account. Your login info is already populated or should be.
Click Next.
Here's another "important" step.
Click on Change Stream... and choose Trainz PE from the list. The list will default to the last one you used.
After choosing the one you need, aka TRS22 PE, click Done.
Close the settings window and close the Launcher.
Wait a few minutes...
Retry your update again.
If this doesn't work, the alternative is do a fresh installation of the latest version of TRS22 PE.
Go to My Trainz
Go to the Product Downloads section
Download the FULL install.
Uninstall then reinstall TRS22 PE using the latest download.
This installation will find your current data folder for the product and you won't lose anything.