I don’t have this issue with DT3 and Catalina - but it’s related to a problem I had with Tinderbox on Mojave. If you once deny the app permission to access Reminders, there isn’t any option to change your mind later.
You might be able to resolve this using Terminal and tccutil, as described at the bottom of the page here
That seems interesting - thanks. Not exactly sure yet which security setting to reset and thus the syntax of the needed tccutil reset - but I will look into that.
I know there were some problems with the web clipper script that seem to be fixed now. I don’t use the reminders script. I honestly can’t remember if I used the web clipper script or just added the clip to DT button into Safari but that is all I ever use and it works just fine on Catalina. I never use Chrome, sorry but web clipping is great under Catalina in Safari.
The problem currently is with the Chrome extension for web clipping.
Absolute worst OS I have ever used. Downgraded for sanity’s sake. I really tried to make it work.
MATH PUNS!
On the subject at hand, I’ve had a laundry list of issues since upgrading to Catalina where prior I rarely ever had any trouble with macOS. Issues include the escape key intermittently not working on the touch bar, random issues with zsh and ruby (some of this was configuration issues that were more forgiving on High Sierra), but most egregiously is iCloud Drive sync completely breaking between my devices suddenly and without warning. I’ll definitely be looking at alternative sync solutions now.
The Windows Vista comparisons I do agree are overblown. It was a little ridiculous to get a million prompts when first upgrading, but from there it’s been nice to know when apps are requesting access to other apps or folders on disk.
The worst part is having no downgrade path and feeling like I’m now absolutely stuck with terribly buggy OS software with no way to install anything else! That being said, it mostly works, so I guess I’ll just have to live with it for now.
I am trying to work out though whether some issues are due to the OS or the apps I am using? I find DEVONthink 3 is seamless as is Alfred which I loaded in place of Launchbar after getting really frustrated and not being able to put my finger exactly on why. I was constantly redoing things and not being able to find places I used to, ironically I find Alfred already a lot more congenial.
This is a bit of a challenge how do other folk go about doing this? Is there a simple method? I doubt it. @tjluoma or @JohnAtl I am looking at you. 
Yeah @rkaplan and @iPersuade I had issues with the DEVONthink 3 clipper. DEVONthink 3 guys say it is a OS issue. You can try, it worked for me, well a similar problem, to restart in Safe Mode and click permissions and then restart normally and don’t toggle extension permissions in Safari. I find Safari fine. I have Chrome loaded but I only use it sparingly.
Is there a simple way to determine whether the issue is with the OS or with the apps?
Not that I’m aware of.
If it was working before Catalina, and now it seems less reliable, then it’s probably Catalina’s fault. 
The only way to really know is to get in touch with the developer. They are in the best position to know if Catalina is likely to blame.