If Mobius is stuck on the processing screen it may be that the start date for payments are set really far back and/or you may be accessing the Sage company data over a network.
First set a custom sync start date to a date around a couple days back from today and leave the payment sync to run overnight. This should resolve the issue
If you are accessing the Sage company data over a netowrk there is typically nothing we can do to resolve a partner's internal infrastructure, but we can suggest that you run the integration on the server hosting the Sage company data to mitigate any networking latency issues.