@Goofus I would recommend TL-SG1005P (an unmanaged PnP switch) connected on its port 5 with the er7212p WAN port.

@Goofus According to its data specifications ZLT X17 power consumption is less than 18W (DC 12V/1.5A or PoE), Power budget of TL-POE50S is 15.4W (Max. 48VDC), so ZLT X17 operates at the limit of its...

@Nick_F That's a good idea - testing the setup with the TP-Link switch excluded. Thus, you'll going to determine whether the issue is caused by the switch itself.

@EricaDalton The TL-SG108E is actually an easy-samrt switch providing WebGUI for configuring the switch features - details. The default username / password for the TL-SG108E WebGUI is admin / admin....

@Tareqsiam If you forgot your administrator pasword, you have to reset the router to its factory defaults and re-configure from scratch.

@Nick_F There's no reasonable explanation for this behavior. I would suggest to change the IGMP version to v3.: Reboot the AX73 and test again.