My problem is solved!
Factory reset makes parameter 0051 0001 and this causes the problem. There is a way to return the value to 0000.

Serial port is still working, I could send a query and get response.
You can open serial port with terminal settings 9600bps 8N1.
and with this order.

~M00910001.
~M00510000.
~MA5F0506A.
~M00910000.

This sequence solved my problem

1. Start configuration mode
2. Set paramater 0051 to 0000
3. Save user parameters
4. End configuration mode

Hello, I have same problem too... I have found https://www.tinytronics.nl/shop/index.php?route=product/attachmanager/getfile&product_attach_file_id=1443
. Reader reacts to all barcodes in this PDF as expected and also does the functions (i mean closes/opens the lighting and cancels/enables reading some type of barcodes etc... but no info comes out from the serial port) .TX signal is not working in any baudrate. How can we get serial port on again! First suhsuh's post is 3months old. I am not sure is there any official support on this forum :/