- yellow LED status on for 3 secs
- yellow LED off for 4,4 secs
based on your decription , Maybe your module has enter PSM mode
pls reach to support@quectel.com ,we need more logs and details.
Please pull up the USB_BOOT pin to VDD_EXT with 4.7K resistor you will find QLdownload port use same port to upgrade the firmware to solve this issue.