Can a sub-account user view the submissions for a form that they have been given access to?

Yes, when you check the "View Submissions" permission. If it's unchecked, the sub-account can't view the form submissions.

Hi,
Thanks for your prompt response.
I've done that for some of the forms that I've shared with sub-users.
However, they still can't see/download submissions. I've attached
screenshots and the actual csv file. Please help...
Thanks,
Khalid
...

EU accounts now have EU data storage enabled by default.  Your account currently does not have this option enabled:

Either enable this option in your account or disable it in the sub-users accounts.  Once the accounts both have the same setting, they should be able to view the submissions.