Are the features you are referring to addons?

If so, they were probably disabled in the update because they are unsigned addons. Firefox automatically disabled unsigned addons for user security.

Please refer to this Mozilla support article for more information about unsigned addons and how to enabled them:

• Add-on signing in Firefox

Thanks for trying to help me, but it's a no go. Read the article, said: in ff43 if you reinstall addons that aren't signed they will be deactivated. Now my Last Pass isn't even there anymore. What a mess, I've spent all evening trying to do system restore to get my computer back to the way it was. Now I can't even fill forms automatically. So many things that saved me so much time are now gone. Why can't Firefox leave well enough alone. Why was I able to use these features for at least five years or more and all of a sudden they aren't safe. Really not sure what to do. Forums never help me because you get a dozen different answers from different people and usually nothing works. This is like every other software or hardware company - when you have issues there is no one you can email just to get an answer. You have to hunt around for hours trying to figure it out on your own and all it does is cause a lot of stress. Have to vent because I'm really angry.

Cool Previews was removed by it's programmer.

Their site says it can still be used but that they won't support it anymore. I want to use it. I'd also like to know how to get my Last Pass back, I've tried several times to uninstall reinstall, etc. It won't install it just says "a few more seconds" doesn't do anything.

Wesley Branton said

Are the features you are referring to addons? If so, they were probably disabled in the update because they are unsigned addons. Firefox automatically disabled unsigned addons for user security. Please refer to this Mozilla support article for more information about unsigned addons and how to enabled them:

• Add-on signing in Firefox

How do I use Cool Previews using this: Have no idea what any of this means, can someone tell me the steps and exactly what to do using about:config as one of your articles said to do.

"To add a new preference, right-click anywhere in the list of preferences. In the context menu, select New, select the type of preference you are adding (String , Integer , or Boolean) and then follow the prompts to enter the preference name and value.

   String is any sequence of text
   Integer is a number
   Boolean is true or false"

Allow me to explain the steps required in more detail:

1. Enter about:config into your Firefox address bar
2. Click the I'll be careful button
3. Find xpinstall.signatures.required in the list
4. Right click the preference
5. Select Toggle until the value is false
6. Then enable the addon from the addon manager

I never used Cool Previews, but from the description, Interclue seems similar:

https://addons.mozilla.org/firefox/addon/interclue/