If you use a multi-band RTK module on your drone then you can’t use the Reach RS+ as a base since Reach RS+ is a single-band receiver that sends only L1 corrections.
We have this support tip that talks about using a multi-band receiver as a base and single band receiver as a rover and the other way around:
You can change the base with a multi-band receiver. Another workaround, as mentioned before, is to use the NTRIP service or download a CORS log.