https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/ Is this the adblocker you are talking about?

I clicked on this link and all it did was download Firefox again. I had Firefox and still have it but the Adblock Plus icon that was installed on my Firefox is still not there. I had it installed and it disappeared. Firefox didn't just the icon for Adblock Plus. It was shaped like a red stop sign with 6 sides and the initials ABP was inside. The icon is still on my Microsoft edge.

"I clicked on this link and all it did was download Firefox again." Open the link in Firefox, if you open it on another browser the button will ask you to download Firefox first since it is a Firefox extension. See screenshot.

If the button says "Add to Firefox", it isn't installed. If it says "Remove", it is installed. What does it say?

You can also check for Adblock Plus in your extension list (Extensions icon -> Manage Extensions, or go to about:addons in a new tab). It may be disabled; if it is, re-enable it by clicking on the toggle.

"The icon is still on my Microsoft edge." I assume you are saying you installed Adblock Plus as an extension on Microsoft Edge as well. That shouldn't influence whether it is on Firefox, since they are on separate browsers.