Post Cover - Can't assign or drag

Hi Guys,
Today I'm working on installation https://www.medservicerepair.com/
(But I've been told we have same issue on lukeroofing.com which is set in your licensing area (I can't seem to find where to add medservicerepair.com))
I created a new post called "Advantage Plus PM". It's now in drafts.
But when I go to drag an jpg image to "Post Cover" nothing happens.
When I open Chrome's dev console it does display an issue. It says:

===========
JQMIGRATE: Migrate is installed, version 1.4.1
index.php:1 Unchecked runtime.lastError: The message port closed before a response was received.
plupload2.min.js:1 POST https://www.medservicerepair.com/administrator/?option=com_easyblog&task=media.upload&tmpl=component&lang=en&&sessionid=730f3fdec8a0b3d855fd56db5adf4aac&7170e851c637d835f6b9ae7b3bec8dac=1&key=_cG9zdDo3MA-- 500
send @ plupload2.min.js:1
exec @ plupload2.min.js:1
shimExec @ plupload2.min.js:1
exec @ plupload2.min.js:1
n @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
send @ plupload2.min.js:1
a @ plupload2.min.js:1
l @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
inSeries @ plupload2.min.js:1
dispatchEvent @ plupload2.min.js:1
trigger @ plupload2.min.js:1
i.trigger @ plupload2.min.js:1
i @ plupload2.min.js:1
start @ plupload2.min.js:1
FilesAdded @ composer-6.0.5-basic.min.js:1
(anonymous) @ composer-6.0.5-basic.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
inSeries @ plupload2.min.js:1
dispatchEvent @ plupload2.min.js:1
trigger @ plupload2.min.js:1
i.trigger @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
setTimeout (async)
e @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
inSeries @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
inSeries @ plupload2.min.js:1
addFile @ plupload2.min.js:1
r.ondrop @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
t @ plupload2.min.js:1
inSeries @ plupload2.min.js:1
dispatchEvent @ plupload2.min.js:1
trigger @ plupload2.min.js:1
n.trigger @ plupload2.min.js:1
i @ plupload2.min.js:1
(anonymous) @ plupload2.min.js:1
Show 35 more frames
VM1086:1 Uncaught SyntaxError: Unexpected token < in JSON at position 0
at JSON.parse (<anonymous>)
at Function.d.parseJSON (jquery.min.js?ad2e39ca43a183af5f0813a94197542f:2:80172)
at Function.a.parseJSON (jquery-migrate.min.js?ad2e39ca43a183af5f0813a94197542f:2:3813)
at C.Uploader.Error (composer-6.0.5-basic.min.js:1:546821)
at C.Uploader.<anonymous> (composer-6.0.5-basic.min.js:1:545885)
at C.Uploader.<anonymous> (plupload2.min.js:1:112955)
at Array.<anonymous> (plupload2.min.js:1:18406)
at t (plupload2.min.js:1:2467)
at Object.inSeries (plupload2.min.js:1:2502)
at C.Uploader.dispatchEvent (plupload2.min.js:1:18440)
======================

I also tried doing manual upload in media.
It uploads the file but then it can not be viewed or selected under "This Post" > "My Media" .
It just spins.