“Adobe Illustrator CS5” needs to be updated.

CS5 is a 32 bit application which will no longer work on the current Mac OS.

You went to Catalina? If so you need to buy all new apps. 

To be honest, why would you not want to update your version of Illustrator to the current?

Do not get me wrong, I completely understand if you do not want to get a subscription to the Creative Cloud.

However... you are really missing out.  CS5 was released in 2010.  Since the release of CS5 there have been so many amazing updates and new tools! 

The bad thing is you are missing out on all those cool things that could potentially speed up your workflow and allow you to create some art in easier steps.  It is something to consider, because I doubt software that is 10 years old is a priority when it comes to creating an update.  The other great thing about joining the Creative Cloud is you get updates and bug fixes.  With older software that just does not happen. 

Plus, most tutorials you find online when you want to learn new tricks are not going to be featuring CS5, but the latest editions of the software.  Thus, you might fall behind your peers.

Just something to consider.  No pressure.... I am sure you have your reason for wanting to remain with CS5.

What System are you using?

Illustrator CS5 will not be updated, only CC versions are getting updates.

If you want to keep CS5 running, you will need an older MacOS