Hi Dauphineo,
Using RMS over VPN may need some configurations in VPN/Network settings related to Packet Size and MTU values.
Details about the process and the required values can be found on the Knowledge Base link shared by Gaurav.
The link can be accessed only after logging-in to the portal.
Please confirm if you are registered on our Customer Portal. If not then please drop an email to crmprod@gemalto.com mentioning your organization name (account name registered with Gemalto).
If this configuration is needed for any third party application that uses RMS, then please get in touch with the application vendor for the same.
Regards,
Ashish