[Obsidian Dragon]

Ok. I may be reading your post wrong (If I am, please forgive me.). It sounds like you downloaded the Protools 2018.1 installer (twice), and When you launch Protools, it still shows version 2018.3 in the bottom right corner. Is that correct?

The part that I don't read you doing is "running" the installation process to overwrite the currently installed version of protools. As some have stated, it is recommended to delete the current installation of Protools before installing a different version of Protools. This used to require an uninstall program but I think for a simple 2018.3 to 2018.1 downgrade, you can simply deleted the Protools application from your "Applications" folder (others can correct me if they disagree). Afterwards, you run the Protools 2018.1 downloaded file to run the installer. When it completes, then launch Protools and verify the version that is installed.

To reiterate, simply downloading Protools 2018.1 does not updated the installed version of Protools. You must run the installation from the downloaded file. Does that sound clear?

I hope this helps