This is Rae from Shopify. Welcome to the Community. I'm happy to lend a hand to make sure you're able to download this app correctly.
What's the name of the app you're trying to download? Is it from the Shopify App Store?
Where are you seeing the 'server error' message appear? Is this happening on the App store, or in your Shopify admin? Can you please reply to me here with a screenshot of this error?
Once I have these details, I can continue helping out.
I hope to hear back from you soon!
Thanks for jumping in and sharing these details. Are you also receiving a 'server error' message?
If so, what browser are you using on your Mac? If you're using Chrome, make sure it's up to date by following these steps.
To confirm if the Mac version is causing this issue, I recommend using a web browser on a mobile device to log in to your Shopify admin and try to download the app you're looking for.
Equally, if you have access to another desktop computer that doesn't have the updated Mac version installed, please give that a try, too.
Let me know how this goes!