GL-AR750S-Ext Extender Mode UI does not load in browser, but UI loads in WDS Mode

Dear Colleagues,
I acquired a GL-AR750S-Ext two days ago and I have updated the firmware to the most recent version.
I have noticed that when configured to the Extender Network Mode, the UI does not load in the browser (Chrome, latest version in Windows 10, latest updates), when I use the IP addresses for this device as reported in my primary DHCP server router.
I have noticed that when configured to the WDS Network Mode, the UI does load in the browser when I use the IP addresses for this device as reported in my primary DHCP server router.
WDS is not supported by either the Verizon FIOS Quantum Gateway nor the Netgear Orbi RBR850 WIFI6 Mesh Network that I have, both updated to the latest firmware versions. It is supported by another WIFI4 router that I have, but I want to retire this router because of security issues and RF spectrum consumption issues. This router is how I am able to test the WDS Mode.
This appears to me to be a bug. How do I upload log files if I cannot access the UI when in Extender Mode? The log files appear to me to be deleted after a reset to factory defaults, which is my understanding the process for starting over when one lose access to the UI. How does one preserve the log files when in Extender Mode without access to the UI from a browser?
Thank you in advance for your reply.

In extender mode, AR750s using relay to implement the bridging. Itself still works in router mode.

So if you want to access it via the IP address, it is accessing from WAN and is rejected. You can open port 80 on AR750s before setting up extender mode.

Dear Colleagues,
Thank you alzhao. Opening up port 80 worked. I am now able to open the UI.
I have set the GL-AR750S-Ext static ip address to an address within the main 192.168.1.x range and the UI opens at that address when in extender mode. However, the main Verizon FIOS Quantum Gateway reports that the GL-AR750S-Ext is at two DHCP addresses, one blocked and the other active, and the Netgear Orbi RBR850 to which the GL-AR750S-Ext is wireless networked with reports just the active DHCP address for the GL-AR750S-Ext. The GL-AR750S-Ext static ip address does not appear in either the Verizon FIOS Quantum Gateway or the Netgear Orbi RBR850 routers connected devices lists.
How do I make the GL-AR750S-Ext static ip address appear in these routers connected devices lists?

Dear Colleagues,
How do I access the UI when the computer with the browser is not connected via one of the RJ45 jacks on the front, such as via WIFI? I must either be connected via one of the RJ45 jacks, or connected to the WIFI on this router. My other routers are accessible via computers attached within my home network. How do I connect to this router from computers that are attached to other routers in my home network?
Thank you in advance for your reply.

Confused. You said you can access the router via your main network.

Can you give more details? What is the DHCP address?