I simply can’t believe a chip that costs hundreds of dollars could be broken easily in that way ). Then I do a simple internet research about Ublox ZED F9P module that installed in the Reach M2. I think I found a hint to my problem in the ZED F9P Integration Manual document (https://www.u-blox.com/en/docs/UBX-18010802).
Referring to section 3.8.2 Antenna short detection - ANT_SHORT_N, it is mentioned that the short antenna will keep being reported as shorted unless the antenna short detection auto recovery is enabled.
I think it is definitely what is being happened to my Reach M2 receivers. The antenna status keeps reported as shorted in the Ublox module, so it won’t receive any GPS signals although the short antenna has been fixed. The antenna short detection auto recovery must be enabled in Ublox configuration, so the Ublox module could receive the satellite signals back.
Please kindly check the document and do improvement regarding this issue in the next firmware update. Maybe this incidence would be happened to other Emlid customers too in the future.
Thanks for your help. These Reach M2s worth a month salary of mine ))