Exactly. There is a comment in the code (in Russian, I think) that explicitly states the current solution is a makeshift and more thought must be given to make TO work properly on multi-display systems.

If this is a laptop, detach all the monitors and you will see TO working again (which proves the point, but is surely not a solution). 

Then, we either wait until the Author fixes this problem or allows for the project to go Open Source.

I don't think laziness was implied. But it does seem that progress is slow (reasons aside). Also, some peculiar behaviour reported by multiple users (myself included) leads, I am quite sure, to local debugging of the extension to find out the root causes. I have done it, surely others did the same. Since I can read Russian, I could find very interesting comments in the code. Clearly things are known to the developer, but still not addressed. Therefore, it would be so good to open source TO, so the community could develop it to the shape it deserves. TO has tremendous potential, yeah?

Do you have a multi-monitor setup?

Well... I guess he made it a bit too easy to get most of the features one may need. So, why bother paying. Or, he should have made it donationware, etc. with some prompt popping up from time to time encouraging to give support (not necessarily a fixed price). VB-Audio (voicemeeter) guy does just that and - I think - he does not complain.

So, if out TO author got frustrated or something - maybe he should re-think his busi9niess strategy.. hmmm....

@Boris: What about just now (for the past few days)?

By the way: I am currently at Chromium ver. 89.0.4389.90 (Official Build) Arch Linux (64-bit)

@Hikari: OH YEAH! That's what I was hoping for. Got it all back. Thank you so much.

I sort of expected major issues with TO at this time, but let me put it in a separate thread.

@Hikari - thank you very much. I perhaps forgot that I actually got something in a form of an URL along with the license. It seemed to somehow work "automagically". I will look for it in my email. 

Still - quite sad TO developer did abandon his werk of art. So many people would be happy to support him (also financially, I presume) if he wished to continue.

Well, well... I am not sure what happened, but I updated Chromium to the latest version and the browser said that TO extension is damaged. Needed to be "repaired". Went ahead with the repair process and it now works again. BUT! Invites me to pay for the extended features again. It does not believe I already did that in the past. Any way to rectify this?  

Not to mention that I suddenly started experiencing the multiplication of tabs in groups. Maybe I must stop Chromium from restoring the tabs on startup.

Except... this is hardly a solution. As the author stated: more of a [temporary] workaround.

TO developer / maintainer should issue a proper fix for this.