I have followed all of the instructions about enabling cookies so that my email address will appear in the Reconnect to Sync box. It appears for about 5 seconds and then disappears. I've repeated the necessary actions again and again, but I can't get the Sync to work any more. This problem is with my iMac, which has been updated to Firefox 56.0. (The Sync works fine on my MacBook.)

Separate problem: My Outlook Mail program -- which is one of the "home" pages I use with Firefox on the iMac -- does not work any more since I updated Firefox to version 56.0. I can't read, send or delete emails. Once again, everything in Outlook Mail still works on the MacBook, which also is updated to Firefox version 56.0. Should I send a separate inquiry to deal with this problem?