This issue has been seen before where the users weren't automatically added to the relevant Sage 200 Active Directory groups during the site provisioning.
NOTE: If you find that the users setup in the Sage Provisioning Portal aren't part of the Active Directory group they should be in Azure, don't manually assign these as it won't pass on correctly into the virtual machine environment. This should all be carried out by the site being created in SPP and require no manual changes in Azure, see below.
If the system is prompting for administrator credentials in the setup described above, follow the steps below.
TIP: To get to the site details page, click the Sage icon top left of the website, then click the name of the site required.

If the issue remains, try unassinging the user from the site and assigning again, steps on how to do this can be found here.