How to get Quick index installed

Using Extension manager, I want to remove Quick index pro, because I don't have a valid subscription
The error message says: Could not find an extension to uninstall.
If I want to install the free version of Quick index The message says:

Momenteel is de PRO versie geïnstalleerd.
Door te upgraden naar de meest recente GRATIS versie, gaat er functionaliteit verloren.
Indien je alle functionaliteit wilt behouden moet je een PRO versie aanschaffen.

Om naar de GRATIS versie te kunnen upgraden, moet Quick Index eerst gedeïnstalleerd worden.
Fout bij het installeren van pakket

SO: From pillar to post

WHAT TO DO???

Regular Labs Extension Manager Component Actie Log Plugin 8.4.1
Joomla De momenteel geïnstalleerde Joomla! versie is "‎4.3.4" ‎

I have gone thru the 'discover' feature before, but I did it again and here are the results:

Er zijn geen ontdekte extensies om te installeren.

Ontdek extensies die het normale installatieproces niet hebben doorlopen.

Excuse me, but I spent so much time to get rid of this 'pro' version, which does not exist, with no result. Regular labs sends me from pillar to post, and because of your native language (I think) 'van het kastje naar de muur'.

Unfortunately I cannot find where the information is stored that I should have installed a QuickIndex-Pro version, which is not correct. Pls give me a hint

I am sorry, but the folder you mentioned does not exist in the (development)domain where the problem is. I copied this folder from the (on-line)domain, where I have installed the free version of Quick index, to the development)domain where it should be. Of course this is not the method how to do it, but i tried and YES the wrong situation still exists.

Somewhere must be a place from where Regular Labs receives the wrong information that a Quick Index Pro plugin is installed.

My next try

I removed everything that I installed from Regular Labs using the extension manager. Hereafter I removed manually all what was left from Regular Labs (Peter van Westen) in the row of extensions.
Then I downloaded Regular Labs extension manager and installed it. And guess, Quick Index pro was shown as the only installed extension but how?

Do you have an answer?

The 'problem'exists in subdomain J42. Subdomain HorizonQuest, which is an older copy of J42, is oke. Subdomain J41 does not use Reg Labs plugins

Thanks
I am a little surprised, because during my trials, I removed the folder /administrator/manifests/packages/quickindex too. The .xml file is a part of the folder.
However, the problem is solved and that was the reason for contacting you.