Hi, 2 possible solutions for you. either of them should work.
1. You will probably need to adjust the application permission in Entra. Add Presence.ReadWrite.All permission
Applications-> App Registration -> 3CX Phone System -> API Permission (see snapshot)
2. In Entra delete the 3CX App and perform the integration again in 3CX. Before doing the integration again, make sure you have both presence checked under users -> Ms365
Hamun.