No idea, does the mouse cursor always change to a link? or are you clicking on text that looks like a link but is not.

Text that looks like a link but doesn't open the browser when clicked on is often due to the message being sent from a mobile device mail app. When the sender types the link directly, e.g. http://www.somedomain.com instead of embedding it in text, e.g. SomeDomain, the link is not clickable when read in TB - although it may be clickable if read through webmail.

First, Thanks for the response.

This is an intermittent problem - that happens over and over and each time lasts for as long or longer than 24 hours, then the links work again. I don't have any mobile devices, and the links are in emails from sellers with whom I deal. If I copy the URL it opens just fine in Foxfire. I am ONLY using a computer running WIN10 OS. I also only use the same email addresses for incoming mail, and both of the accounts don't function simultaneously when this "issue" is happening. AND, I don't think it is computer related, TB is the only thing "acting up" when this happens!

And year, I know it if Firefox, not Foxfire - I have a migraine and mentation is skewed. That is an ooooopsie!

Just to clarify, this has nothing to do with your mobile devices - it's a well-known issue with senders who send links from their mobile devices that aren't clickable when you read them in TB. Since you say this happens intermittently, it could very well be due to some of these sellers sending mail from mobile devices. You might get a clue by viewing the message source (Ctrl+U) and looking for the User-Agent header that indicates the mail app or operating system.

If the issue is not due to mobile mail apps, I wonder if you have some security program 'sanitizing' messages with links that are deemed 'suspicious'.

I don't own any mobile devices (I live in the mountains and they don't get signals here!) and the messages containing links are not sent from mobile devices, but from major companies I do business with online and who regularly email me with links for special offers - and the links work MOST of the time - but then from time to time the links don't open in Firefox and I have to copy the URL and paste it in FF. The email providers (2) that I have attached to TB do not end up putting these messages in trash, spam, or anything like that. I go to their websites and periodically empty all the message boxes. One of them regularly blocks things but send me emails to tell me they've put something in "Spam". The other company has no "spam" and lets everything through but occasionally asks me if I wish to go to the site or blocks elements in the emails and I have to choose, "Show remote contents in this message" (under “options” when I choose one to view of those emails). If clicking on the links NEVER WORKED (the bold and italics for this response box act funky, hence the upper case) I would not be used to clicking on them. ALL of them suddenly become un-openable by clicking, then after a period of time - from a day to several days clicking on links suddenly starts to work again sometimes for as long as a couple of weeks. This change seems to have NOTHING to do with how many messages may be stored by the email providers since emptying everything does not alter the problem WHEN it is happening. It just comes and then it goes - but clicking probably works 80-90% of the time. But when it doesn't work, it doesn't work for ANY link. I do not know how else to explain this - and I don't see how any setting or security systems are the issues - because it is intermittent!

What about an anti virus program... they have a nasty habit of partially dying and the firewall component prevents mail downloading, or the url inspector part goes to god.

Does the issue continue after you reboot your computer?

I don't leave my computer on all the time, so I reboot on average of 3X a day. Reboots do not change anything. Mail downloads fine - the only problem is with links contained in the emails. I hate intermittent problems. This is like, "My car is making a funny noise, but it's not doing it right now - while you're listening." It is the intermittency that is weird - and what I can't seem to sort out.