Well, yes.... "AT\r" should be enough and this was even mentioned in the datasheets.
Anyway, mostly people use tinyGSM and "AT\r\n" should work anyway.
I tried "AT\r" - no difference, the modem remains silent. I also tried a USB-USART connection with 3.3V levels and tried different baudrates, spamming the modem with any combination of "AT\r\n" - no success.
Normally it has autobaud, if not it should start with "RDY" - I'm not getting anything with powerup. The modems LEDs blink but thats all.
I saw that they're translating the logic-levels from 3.3V to 1.8V. I'm not sure but these are looking completely strange to me.

There shouldn't be any 3.3V peaks, right? The image shows my TX line, somewhere at transistor Q3. NB_RX and U1_RX are looking quite similar, so maybe the transistor is broken?