I also have the same problem but the customer service does not answer the mails or the questions on the forum. Maintain that the product is sold they do not care about the customer !!!!
Look at the Serial Number information. If the first four digits is A912. You've applied the wrong firmware. The latest firmware for GT1 Standard starting with A912 for S/N is just 111M0. Simply downgrade to 111M0 and all will be back to normal. :)
Beelink GT1 Mini (95X2) w/CoreELEC & Android 9 (Pie)