By default, WHMCS does not allow dependencies between configurable options. If you have a product where the customer can configure the server himself, this can lead to invalid configurations.
We offer an additional module where dependencies between configurable options can be created. You can find more information here:
- Dependent Configurable Options For WHMCS - Documentation
- Dependent Configurable Options For WHMCS - Order link
If you have any questions about the dependency module or you are not sure if it fits the purpose, feel free to contact our support.