
Hi, @AH-31052106-0
Let's first check licensing: Probably, an E3 license plus Dynamics 365 Sales Professional gives access to apps, but not automatically to environments. To see environments, the license must include a recognized Power Platform or Dynamics 365 service plan (troubleshoot).
Second, the environment security group: If the environment is tied to a security group, the user must be a member of that group. Otherwise, the environment won’t appear in their list.
Third, the security roles: Let's make sure, the user needs at least one Dataverse security role assigned in that environment (e.g., Environment Maker, System Administrator, or a custom role), even we have the right license.
Finally, Let's use diagnostics tool: Power Platform Admin Center has a built-in user access diagnostics tool that will flag missing roles or group memberships. You can give a run.
However, I suspect, in your case, the missing piece is almost certainly a security role assignment in the environment. Without it, the user won’t see the environment even though they can sign in.