Hi there,
Per this document https://developers.hubspot.com/docs/api/working-with-oauth
users can install app if they have App Marketplace Access permissions.
In our app, we required “tickets” scope and granted a user tickets and App Marketplace Access permissions, but he still can’t install the app, the error says “Couldn’t complete the connection You don’t have permission to connect this app.” Not sure what happened, what permissions shound be granted to the user if the app requires “tickets” scope, any help is appreciated.
Hi @LianYiFei 
If the given HubSpot User has the “App Marketplace Access” permission enabled (or if they are assigned as a Super Admin) within the HubSpot Account they wish to install the given app, they should be able to install it without any problem.
I’d suggest double-checking your user permissions (as above) and making sure you’re using the current version of your app install URL (this changes when you update required scopes).
I hope this proves useful. Please let me know if you have any follow-up questions.
Hi @zach_threadint Thank you for your reply, I’m sure the install URL is correct, the problem is we don’t want to assign the user as super admin, wonder if there is a way for common user to install an app that requires “tickets” scope?
Hi @FelixLian @LianYiFei
I see, and yes I’ve been able to replicate the issue you’ve described. If the permission “App Marketplace Access” doesn’t work, the only advice given by HubSpot (as far as I’m aware) is to set the User as a Super Admin. Sorry that’s not the answer you were likely hoping for. Hopefully I’m wrong or things change soon
I hope this proves useful. Please let me know if you have any follow-up questions.
@zach_threadint Thanks for your help, Hope someone official can confirm this issue. Do you know the support email I can reach out to?
@FelixLian I don’t have any specific support email addresses for you. Information about how HubSpot Support works (e.g. subscription levels required for Live Chat support) can be found here.