I want/need my Adobe Acrobat X Pro to work

I agreed to load the Adobe Fill & Sign app via the 7-day free trial.  Interestingly, I witnessed a number of "add on" apps in my Adobe programs.  With great regret, the app never worked so I canceled the subscription before the end of the trial a couple days ago.  Today I tried to use my faithful Adobe Acrobat X Pro to combine some files into a single PDF.  The pop-up says I must use Adober Reader DC.  Wrong answer!  How do I get my Adobe Acrobat X Pro to work again?

Very frustrating!

Thanks