I had version 45 ESR installed. I had the Selenium IDE plugin installed and it worked. I was experimenting with other FF versions (55, 54) to see if they work with the Selenium IDE. I installed the ESR version 55 and it worked. I installed ESR version 54, it worked. Everything seemed to work. Then I uninstalled the Selenium IDE. I have gone back to version 45 and it says that, "the Selenium IDE is incompatible with this version of FF". Selenium IDE is the only reason I have FF. How do I fix this?

By the way, whoever thought that this was a good idea is gravely mistaken. It works with version 1, version 2, version 3, version n - uninstall the plugin and even if I go back to version 1 I cannot install it? Bad programmer!