Solution: Remove the icon cache file
Adobe is working to resolve the issue. Meanwhile, follow these steps as a workaround:
Open the local appdata folder:
C:\Users\\AppData\Local\Adobe\Acrobat\DC
Delete the following file in the local appdata folder:
For Acrobat Reader DC: IconCacheRdr.dat
For Acrobat DC: IconCacheAcro.dat
Relaunch Acrobat Reader DC or Acrobat DC.
Note: Before clearing the cache file you must close Adobe Reader which is very important or the issue will still exist.