Suddenly you get the JLIB_APPLICATION_ERROR_COMPONENT_NOT_LOADING all over the place - frontend and backend alike? And you searched the web and get all sorts of confusing tips?

Look no further - at least until you did not tried this simple trick! (Especially if you just relocated your site recently - or your hosting company did it for you). If you have plenty of space, check the following tip too.

Clean your cache. All sorts of caches. Go to Joomla's Cache manager, and purge it. also be sure, that you purge also the expired cache.

Next check, if you have some other caches to clean. Some template vendors are packing their templates with caching functions (probably the most notorious is JoomlArt Cache Manager - but is not alone) - clean those caches too.

Do you use some CDN (Content Delivery Network), as CloudFlare, Amazon S3 or something similar. Go there, and purge the cached things there too!

And, as I promised, in 95% of cases the error will gone.

If the problem still persist after checking to have enough free space and all caches cleared, you can still look for other clues. The possible culprits can be many, trying to enumerate just some: Kunena upgrade on a site using a custom Kunena template, Akeeba upgrade over several versions (you have skipped a bit too many upgrades...), System - pjtemplatetoggle plugin misbehaving and many more. But, again, the main culprits are insufficient available space and an "unfinished" site relocation done by yourself - or by "curtoasy" of your hosting company.