Hl78 no at response to mcu through uart 1

I currently have my stm host device connected with the hl78 through uart1. I have tx,rx, rts, and cts. However I do not get any response back.
When I use the terminal on my computer and connect the usb to the uart1 of the hl78, it works perfectly. Are there any additional set up that I need for an stm host device to work? Any switches or jumpers I need to set the hl78?

if it works with PC UART, probably there is no problem with the module, then you need compare the voltage of those 4 lines

I have yet to check the voltages, but I was wondering if there was a specific character that I needed to end the string when sending an at command over uart? Like do I end the string with a ā€œ\r\nā€ to indicate a return or do I need a ā€œ\0ā€? I have tried all of those combinations at the end of the string but is there something I am missing?

you should be able to find the answer in the case in your PC, right?