On 1st January 2023 Microsoft implemented a change so that new Exchange Online tenants in some cases create inbound connectors in disabled state.
If you selected the option to use server-side signatures in Signature 365, the setup wizard will show an information message if the inbound connector is created in disabled state.
To resolve this problem you need to open a new support ticket with Microsoft Support in your Microsoft 365 admin center.
Inform Microsoft Support that you are setting up an email signature solution, Signature 365, which requires an inbound connector to be created in your tenant.
The Signature 365 setup wizard executes the following PowerShell command:
It is this PowerShell command that successfully creates the inbound connector, but in disabled state.
Request Microsoft Support to enable the inbound connector named "Receive from Signature 365" in your tenant.