Walrave, W. (ADM) • Thanks for posting your query on Microsoft Q&A.
#1. Firstly, check if there are any policies assigned to the resource group where you are trying to create the lab. If yes, then ensure that the policies are not blocking the creation of the lab. You can check for built-in policies for Lab services under this section:
https://learn.microsoft.com/en-us/azure/lab-services/azure-polices-for-lab-services#lab-services-should-enable-all-options-for-auto-shutdown
Azure Policy built-in policy definitions.
#2. If you are using lab accounts, try decreasing the lab capacity by 1, then increasing it again. If you are using lab plans, try checking the Quota and Usages blade for Lab Services. You might need to request more core capacity.
#3. If the above steps do not work, you can try creating a new lab plan instead of a lab account. Lab plans have replaced lab accounts and offer more features and flexibility.
Additional reading:
Resolve errors for request disallowed by policy
If you still have questions, please let me know in the "comments" and we would be happy to help you. Comment is the fastest way of notifying the experts.
Please don’t forget to Accept Answer and hit Yes for "was this answer helpful" wherever the information provided helps you, this can be beneficial to other community members for remediation for similar issues.