Your welcome.
Please keep in mind this is'nt Arturia support. I'm a user.
Are you sure your external drive have been given the same drive letter/ id as when you installed? Like if you have had the drive unplugged or have had other external devices plugged in.
You issue can very well be about that. If you use the same letter/ id for your drive as it had when you installed the collection, then it might work without doing anything else.
Here is how to uninstall:
https://arturiahelp.zendesk.com/hc/en-us/articles/4405741261714-How-to-properly-uninstall-an-Arturia-softwareYou have to put the paths you have used instead.
But if the uninstaller can't find the correct path, then you might have a problem in doing this way.
About Activations/ Licenses, then in ASCs prefernces under Licenses you can deactivate all Arturias products on your computer. (But again i can't tell, if your disc issue will give trouble.)
You can also deactivate through your Arturia website account though.
The fact you have 5 licenses does'nt mean you only can install 5 times. It mean you can install on 5 devices at the same time. If you deactivate one, then it's free to be activated again.
Does'nt your product show as activated in ASC? If not, then that might indicate the drive letter/ id have been changed. But i can't tell for sure.
I'm on Windows 10. I think i have seen in a post you are on MAC, and i don't know much about MAC.
Perhaps your issue is a user error.