Just to add my comments, if the APN is set incorrectly - it can be adjusted for the HERMES module in DTS.
I'm not exactly sure if APN is the issue as there is the filtering content which is dictated by APN - I think? Do you even see the 4G/Me indicator on the main mbux system? If you do not me icon then your HU6 is not connected to the Hermes module, the Hermes module connects to the HU6 via a WLAN gateway.
There are many connectivity issues; if the app doesn't report remote states or any data information after the dealer verifies the logbook (e.g. my case) and adds your email to the VIN - then the issue lies with the Hermes module.
Saving codings of Hermes in DTS -> Xentry actual values, see operational mode.
Also check if the vehicle can ring me customer support using me button - if it does, good news - the Vodafone esim is somewhat working.
Now in my case, operational mode was set to crash mode, although, there are other states which can deactivate the data connection. In special versions of Xentry, there is a procedure to set this to the provisioning state. After doing so the HERMES module will re-establish a new VPN certificate for data connectivity to work with the car, the backend has a PKI infrastructure which uses a certificate-based authentication system.
Although, if the vehicle is in a provisioned state, then use DTS to set APN settings, I can't remember if this had per-country configurations but I don't recall there being many APN settings which I doubt is the case as the HERMES module should be able to do roaming.
Some other connectivity issues are that the MBux (HU6) unit loses time sync and the certificates no longer work - in this case, a special adaptation in Xentry resets the clock sync. Another adaptation is that the
HU6 certificate becomes invalid and there's one to restore the initial authorisation certificate. The next time the car requests an updated certificate - it will be regenerated with the correct one for this vehicle. These are HU6 errors with connectivity and not HERMES ones though.
I had some experience with working on PKI backends at work last year and was lucky enough to delve into trial and error - a video from Duoyin with Google Translate helped me on this one
Also, not all vehicles will have the Mercedes Me app on the MBux (HU6) - for example, I am on FUP4 and even with FUP3_4 there was no 'Mercedes Me and Apps' - it was always just 'Apps' on my system. Although, I paid for the personalisation option included in the remote package which allows you to have the 'Me' users within the system as this is not a free feature either. So I wouldn't determine the 'me' sync functionality to be a valid test routine.
Officially, I'm not sure if the Dealer has access to variant coding using DTS - but they can raise requests back to HQ for HERMES issues - therefore, I feel like some of the diagnostic work hasn't been done correctly. It does specifically state in one of the Xentry TIPS documents I located online when I had this issue - that this should be done if there continues to be no connectivity and some packet logs are captured as Xentry can communicate back to the backend with an official dealership account and will report back to the engineer if it can see any packets sent (similar to a wireshark).
Alternative methods used by people on Duoyin also attempted to export the variant coding of the HERMES module, then do a complete factory reset / reflash HERMES and reimport the codings. Which is basically an 'offline' SCN
