Same issue , Re Pick the board and port each time look at the status bar below and see that it reflects the right choice. before and even during the compile and upload. I made a video of it . slow it down to follow along. HERE and my Describing the problem verbiage.
Thank you very much for your reply.
After trying many things, I found that “mbed 1.0.0” is fine, but “mbed 2.6.1” and “mbed 2.7.2” cause problems.
IDE 2.0 still seems to be unstable, so I will use IDE 1.8.19 for the time being.
, follow the Arduino how to for adding them. I believe the Seeed Wiki has the link for the boards, I don’t remember exactly. But it does work very well.
You do have to select the board each time you Compile or upload, verify the connection via the status bar message whether its connected or Not.
HTH
GL