I just updated an "older" Craft site (version 2.4.2702) to the newest update (version 2.6.2958).

But now all my image thumbnails in the back-end are missing and if I upload any new assets, the thumbnail is not generated and I get a Internal Server Error 500 on the front-end as the URL it points to is still the `cpresources/transforms/283?x=qFc4lFWR5` kind of URL.

The image thumbnail itself is also not generated anymore in the folder it is supposed to go in. I didn't change any folder permissions (only updated the new app folder ofcourse with the correct permissions). I'm able to upload assets so the permissions should be fine I guess.

I've had issues like this before, but those were resolved, so I don't know what is causing this issue again. Is there anything I forgot about this update that I needed to change? I needed to do a manual update.

The only logs I get are these:

 2017-01-17 10:13:26
 
 Level	info
 Category	application
 Message	[Forced] Finished task 14 (GeneratePendingTransforms).
 2017-01-17 10:13:26
 
 Level	info
 Category	application
 Message	[Forced] Starting task GeneratePendingTransforms that has a total of 0 steps.

Would it help if I would rebuild all asset indexes? I started that but he couldn't find a few images due to a wrong path and I clicked abort because I was scared that he would loose all image transforms on the site. I was testing on the live site at the moment so I didn't go through with it.

**UPDATE**

I do get a PhP error:

 [18-Jan-2017 14:04:07 UTC] PHP Fatal error: Call to undefined method Imagine\Imagick\Imagick::getImageAlphaChannel() in MY-BASE-PATH-HERE/craft/app/vendor/pixelandtonic/imagine/lib/Imagine/Imagick/Imagick.php on line 191

But through the PhPInfo in the Craft CP I can see that Imagick extension 2.2.2 is installed as is GD as a fallback.

I just clicked rebuild asset indexes on the live CP instead of my local CP by mistake and now all images on the live site are gone. So this just became a serious URGENT issue. :/