I am using the pymakr plugin and created the conf file
I cannot see a "sync" button as mentioned in the docuementation but a upload button is there. Unfortunately it fails on the first file, boot.py:
There was a known issue with the previous version of the firmware that caused this issue. Please try updating your module to the latest firmware (released yesterday) and check if that works any better. If the issue persists please let us know.
You don't need to init UART unless you need different settings.
It is already done in _boot.py, which is called before boot.py.
The second init call was one of the big problems in the 1.10.0 firmware. Sadly the init exist in a lot of example files when you browse for boot and main files.
I suggest to try it simply again. Sometimes it fails on my LoPy too. If multiple tries will not help, erasing the whole flash partition seems to be the common solution for such problems.
You can give secure boot a try, which does not execute boot.py and main.py. This may help if you have a faulty UART configuration. If you have not switched off WiFi, you can upload boot.py and main.py via FTP.
use this code, it will help to initialize the UART
from machine import UART
uart = UART(0, baudrate=115200)