There are a number of steps you need to ensure you have carried out when setting up the RSCM server, one of which is ensuring that the RSCM Service has access to the projects and that users also have access. You shouldn't run the service as a system or root account, you must create a 'user' that can write to the project, usually a 'service account' is one that regular users don't log in with but one that has access to all project accounts. This is documented in the Administrators Guide and there are a number of articles on Microsoft's web site about creating service accounts if security is a concern. On Linux you can create accounts that do not enable login but can be members of the project's group settings.
As a quick test run the service as yourself and see if this helps.
If you don't get very far after checking the admin guide contact your local support office.