I have it running on routeros 7.8:
I used the following at commands:
at@nvm:fix_cat_fcclock.fcclock_mode?
at@nvm:fix_cat_fcclock.fcclock_mode=0
at@store_nvm(fix_cat_fcclock)
AT+GTUSBMODE?
AT+GTUSBMODE=7
AT+CFUN?
AT+CFUN=15
After that, I still had problems. I had to upgrade the firmware of the modem, using the instructions here (using google translator):
https://radenku.com/upgrade-firmware-fibocom-l850-gl-l860-gl/