Question about USB SERIAL read

[OMGlinuxIS]

I downloaded the SerialOTG extension

Serial OTG. Arduino CH340. FTDI. rkl099's Extension

Hello friends, I am going to comment on my experience with the great extension of the user @rkl099, which you can find in this topic: With this extension we can connect a mobile phone (or tablet) to the Arduino with a CH340 chip by cable. It has been tested with CdcAcm, PL2303, PL2303HX, FTDI, CP210x, CH341, CH341 (“fake”) and CH340. Get com.SerialOTG.aix: To carry out these examples I will use a mobile with Android 9, OTG cable, USB cable and an Arduino UNO with CH340. [otg17] …

https://github.com/rkl099/Appinventor-SerialOTG/blob/main/com.SerialOTG.aix

I have a program like this:

But every time it connects when it asks whether to allow connection to "null" (serial) it sends some data and answers itself by typing nickname. The result is 5 diamonds with question marks inside. Someone can solve it for me?