The error: Your request could not be completed. Adobe Acrobat license has either expired or not been activated. Try launching Adobe Acrobat.
If you’re encountering an issue where Adobe Acrobat is showing an “expired” message, it could be due to a variety of reasons, such as an expired trial version, license issues, or a misconfiguration.
While Adobe Acrobat is a paid software, there are some steps you can take to resolve the issue without needing to pay for a new subscription immediately. Here’s an introduction to some free solutions you can try to fix the “expired” issue in Adobe Acrobat.
Note: this problem is Adobe Acrobat cannot combine multiple PDF files in to one PDF file. So when we try combine it will pop up the error as below.

To solve this problem for free, How To Got gives you this best solution. You can use Free Adobe Acrobat and watch here how to install Adobe Acrobat DC.