I used MBED Onlinecompiler with Nucleo-L152RE which is very spread in German schools.
On migrating I observerd the following Issues:
Run-Button exits with RDDI-DSL ERROR: vRviTTAPSeqSim::RunSequence(): SDS_ERR_SESSION_COMMS_FAIL : SDS session comms failed.ErrCode [0x001B] ExitCode [0x0000]
Debug Button exits the same. No debug possible
No possibility to see the documentation of mbedos or other library as possible in mbed onlinecompiler
No possibility to search for community programs or libraries like in the import-funktion of mbed onlinecompiler
alternativ Targert: Target "NUCLEO_G474RE" is not recognized, no build possible
This way Keil-online-studio is a very poor replacement to mbed onlinecompiler.
I had a similar issue using Keil Online Studio with the Nucleo_L476RG dev board. I solved the issue by using the STM32 Link Utility and resetting the board (STSW-LINK004 - STM32 ST-LINK utility (replaced by STM32CubeProgrammer) - STMicroelectronics).