@ethanh100 

The specs show the USB is for media or FTP server. 

  @ArcherC8 I mean the thing literally has the words 3G/4G on it so...

  @ethanh100 

If you have a Mac, The simplest way to create such a setup is to hook an iPhone (or iPad with a similar plan) to a Mac via USB, and share the internet connection via the Mac’s Wi-Fi.

see macworld web site for more info. 

  @ethanh100 how are you connecting the iPhone to the router to supply internet connection?

  @Marshmutt 

See user manual and the connections, hot spot  mode. 

  @ethanh100 

I understand your situation with the TL-WR902AC travel router. While the router does have a USB port labeled "3G/4G USB," it's primarily intended for use with USB modems rather than direct USB tethering from a smartphone.

However, some routers support USB tethering with certain firmware versions or settings adjustments. Here are a few steps you can try:

1. Firmware Update: Ensure that your router's firmware is up to date. Sometimes new firmware versions include added functionality and bug fixes.

2. Router Settings: Check the router's administration page for any options related to USB tethering. This is typically found under settings related to the USB port or internet settings.

3. USB Tethering Mode on iPhone: Ensure your iPhone is set to USB tethering mode. This can be done by connecting your iPhone to the router via USB and then enabling "Personal Hotspot" with "Allow Others to Join" on.

4. Router Documentation: Since the documentation might not explicitly mention USB tethering, sometimes it's helpful to refer to forums or the router manufacturer's support for any hidden features or less-documented capabilities.

If these steps don’t resolve the issue, you might want to consider using the traditional Wi-Fi hotspot method or looking into routers that explicitly support USB tethering with smartphones.

I hope this helps!