Combine files in Acrobat XI pro

[LMPierce]

I've been using Acrobat XI Pro for some time now; however, recently I've been unable to combine PDFs. I get the following:

To the best of my knowledge, the only think I changed was updating to Windows 11.

Any help on how to resolve this issue would be appreciated.

[try67]

You can combine files, but not as a Portfolio.

[JR Boulay]

Flash Player was discontinued a few years ago and Acrobat XI will never be updated since it's discontinued too.