Font has shrunk on restart, can't fix
I run both T-bird 45.3.0 and Firefox 48.0.1 on my 2014 Mac Air/El Capitan.
My laptop was lagging and dropping the network signal, so I shut it down for about 20 minutes. When I powered it back up, the fonts on both Firefox and Thunderbird were reduced almost to the point of unreadability.
Focusing just on Tbird for a moment: I opened Preferences, where everything looked normal. As an experiment I raised the minimum font size up to 24 pts. No change. It's all still miniscule - both the list display and the email contents. (On Firefox, it's the tabs and toolbars.)
I have the Theme Font and Size Changer Add-on. I disabled, re-enabled, removed, and re-installed it. Nothing. I've tried to open Preferences for it but all I get is a radio button list:
- Hide Tools Menu option - Hide App Menu option - Abbreviate Toolbar Button Text
... nothing about the actual font size.
What's gone wrong here, and how do I get back to readable font?
Thanks!
ఎంపిక చేసిన పరిష్కారం
Theme and font size changer has experienced what appears to be a bad update.
On the toolbar 
then 
Remove theme and font size changer.
use the search box in the top right to search for the theme and font size changer. Typing font should be enough to locate it.
reinstall it.
Better?
ఈ సందర్భంలో ఈ సమాధానం చదవండి 👍 2ప్రత్యుత్తరాలన్నీ (3)
More info: the Theme Font and Size Changer icon has disappeared from my toolbars on both Thunderbird and Firefox. I see another user reporting the same thing: https://support.mozilla.org/en-US/questions/1138602
I had the same null response trying to reinstall it.
It sounds now like my restart may have been coincidental to the loss of Font Changer functions.
ఎంపిక చేసిన పరిష్కారం
Theme and font size changer has experienced what appears to be a bad update.
On the toolbar then
Remove theme and font size changer.
use the search box in the top right to search for the theme and font size changer. Typing font should be enough to locate it.
reinstall it.
Better?
Thank you, Matt! TFSC put out a repaired update, I've downloaded it, and I'm back in business. I appreciate it!
Angie