@kaleidoscope , Glad to know that the issue is resolved by upgrading to the Basic tier. Thanks for the update.
As I'd mentioned, to create custom security bindings or enable client certificates for your App Service app, the App Service Plan (ASP) must be in either Basic, Standard, Premium, or Isolated tier, as this feature is not supported in Free or Shared ASP.
In regards to the ASP cost: Your App Service plan can be scaled up and down at any time. By changing the pricing tier of the plan. You can choose a lower pricing tier at first and scale up later when you need more App Service features. Note that you can host multiple WebApps under the same ASP.
Note that since you pay for the computing resources your App Service plan allocates, you can potentially save money by putting multiple apps
into one App Service plan. You can continue to add apps to an existing plan as long as the plan has enough resources to handle the load. However, keep in mind that apps in the same App Service plan all share the same compute resources.
To determine whether the new app has the necessary resources, you need to understand the capacity of the existing App Service plan, and the expected load for the new app. Overloading an App Service plan can potentially cause downtime for your new and existing apps.
Kindly checkout this document section 'How much does my App Service plan cost? ' for more details.
Hope this helps!
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