salamat dito lods, nagtry ako mag downgrade from 3.0.6 to 1.15.1 pero nagfe-fail. Then, nag try ako ng ibang lower version. nakapag-downgrade ako from 3.0.6 to 1.12.8 ng walang admin access. hahahaha. Saka ako nag try mag change ng admin name at password para mag downgrade to 1.10.23. nakapag change na ako ng IMEI at susubukan ko mag lock ng bands. Sa mga gusto i-try yung ginawa ko i-download niyo yung X21G_1.12.8_usr_UN2020C_20220309_normal_update.bin tas rekta upload kayo. Then, follow niyo na ulit yung steps ni OP.
bro, you're trying to downgrade the version from 2.6.6 to 1.10.23. You should follow the steps and start with 1.15.1.
OR, try downloading X21G_1.12.8_usr_UN2020C_20220309_normal_update.bin first then, upload it. Be sure to reset your modem by holding the reset botton for 10 seconds after a successful downgrade. Next follow the instruction from Steps #2-#9.