I flashed the X8R receiver with ACCST V2.1 firmware from X9D Transmitter to ensure latest version was loaded. I selected a Taranis Horus X10/X10S transmitter for this project. The unit I purchased came from ebay and had FrOS installed by default. I updated this to EdgeTX 2.10 Centurion before trying any bind operations. I downloaded the IJXT Module firmware upgrade for ACCST V2.1 and loaded it onto the SD card. When trying to flash the internal module, I kept getting "module not responding". I believed this could have been an issue with EdgeTX not being able to flash internal modules. I decided to reflash the firmware using OTX Companion, using 2.3.15. After reverting, I still could not flash the internal module. I spent several hours troubleshooting and believed the internal radio might be bricked, which was a huge bummer. Thought I may have to flash it directly using an ST Link tool. I know the X10/X10S shipped with an XJT module, but the X10 Express shipped with the newer ISRM module. There is an upgrade module that can be installed to enable ACCESS and ACCST. So I loaded the ISRM firmware onto the transmitter. This flashed successfully. I believe what happened here was the original X10 unit was upgraded with an ISRM module, but this was not noticed or listed by the ultimate seller. The radio itself was not displaying the module firmware, so it may have been flashed incorrectly in the past. Now that the transmitter's internal module has firmware matching the X8R, bind testing can commence.