An issue happens before Adblock Plus is installed or persists if it is uninstalled: you have to look elsewhere for an explanation. In particular, if Adblock Plus fails to install and you are using a supported browser then you are facing a browser issue and the general troubleshooting intructions apply.
"intructions" should be "instructions"
and duplicate sentences:
Any configuration details that might be relevant (filter lists used, own filters if any, unusual browser configuration, other extensions)