what version of RTKConv are you using?
I recently got a response on another thread regarding RINEX conversion for L1 only
Also, I’d like to point out that RTKLib version 2.4.3 Emlid b28 is designed for Reach RS+ and Reach M+ receivers and, therefore, outputs L1 data only after conversion. I assume that’s the reason why OPUS aborted the submitted data.
For Reach RS2, there is an RTKLib version 2.4.3 b31 that can be downloaded from our docs.