Here is some information I passed to another person that helped them.
I had issues also but using the alternate calibration method, things popped right in.
Go to the amateurradiokits website.
You have to go to "My Account" dropdown (Orange Button)
Depending on the login state you may have to login.
There you will find a "downloads" link. (7th down)
Download the "uBitx Nextion Case" (last one, takes a while)
Decompress is and look for a folder called "AGC"
When you get to building / calibrating the AGC board use the "AGC Details.pdf" file found in the AGC folder!
This is a multi-page PDF file.
Look at the entire file, at almost the end of the document is an alternate calibration method. Try that.
DON'T download the second folder down (AGC) from the downloads amateurradiokits website. It will not give you ALL the information you need to know.
I used the AGC folder from the "ubitx nexton case" folder. (Spent a couple of days figuring that out.)
Hope this helps!