Create Azure function app validation failed but no error

I am trying to create a function app, which uses an existing storage account. I am aware that there are limitations on which storage accounts can be used but I believe storage account is suitable and it is available for selection on the storage tab.
I am using an app service plan.
The storage account has been secured with a virtual network and private endpoints (I did not set up the storage account).
On the networking tab, I am disabling public access, enabling network injection, selecting a virtual network and I have configured inbound access.
However, when I try to create the function app, it tells me validation has failed but there is no error! There is nothing in the activity logs, which makes sense since it is not actually trying to create anything because it fails on validation.
How do I find out what the validation errors?
Thanks