Why am I

I forgot to add this guidance: https://helpx.adobe.com/acrobat/kb/acrobat-trial-removed-previous-version-and-plugins.html

Yes, upgrade to Adobe Acrobat Pro DC which is fully supported in Micrososft Windows 10.

Seems like you're using an old and no-longer upported version  of Acrobat Pro which accroding to system requirements, fi that is Acrobat Pro X or XI  seems like you squeezed in tha installation forcibly in your Windows box.

 I would suggest, that if your Acrobat Pro was working before and all of a sudden it's behaving like this, to  click "Help"--->>> "Repair Installation" and then force manually  the last known version update for whatever version of Acrobat Pro you're using.

That is the only work around that you'll see frequently recommended here in the community support forum.

You can get those updates from here: 

• Release Notes for Legacy Products 

In addition, if you're one of those Adobe customers who refuses to give up your old Adobe Acrobat Pro, I would also suggest to run it in compatibility mode.

To do so, right click on the Adobe Acrobat Pro icon in wherever folder you have it installed.

In MS Windows 10 , Acrobat executable for Acrobat Pro DC if installed in this directory path:

• C:\Program Files (x86)\Adobe\Acrobat DC\Acrobat

Check in your system where the executable for your Acrobat version  was installed to.

Scroll down until you find the "Acrobat.exe" file, right-click on it--->> Select "Properties" from the context menu and switch to the "Compatibiity" tab.

See slide below:

Last, verify and confirm that if you've set Adobe Acrobat Pro as the default PDF owner in your system that MS Windows 10 is not reverting the PDF ownership back to MS Edge browser or something else.

Very frequently a lot of users in report back to the forums observing that this isa frequent issue with each MS Windows update  (specially with  unattended system updates).