Using constant contact and firefox 52.0. When setting up a new email campaign I am able to select my email list, but when trying to limit by tag it shows the option of selecting "limit by tag" but when selected no action follows and it does not allow me to actually limit or input the tag name to select the limit by tag option.
I am sorry that the tag functionality in your account is not working properly. I want to help you try and troubleshoot what may be going on. I know that you mentioned you are working in Firefox, have you tried a private window in Firefox to see if that helps?
Have you also tried using another browser to see if it may be happening only in Firefox?
Let me know if you are still not able to get the Tag search bar on the scheduling page.