Reflashing Firmware on Netgear R7000p from MacOS

I have an R7000p that I installed an Express VPN custom firmware to.  After uploading the new firmware, the router boots up and doesn't appear to be bricked, but. . . .

I am unable to ping the router (from either a wired OR wireless connection), and consequently can't get any Internet access.  The router does assign IP addresses, and it's default IP configuration after reflashing is:

Gateway 192.168.132.1

Subnet Mask 255.255.255.0

It will assign my machine (via either Wifi OR hardwired connection) an IP address such as 192.168.132.115

I have tried a hard reset of the router (power on hold reset), and have looked into both nrmpflash and tftp, but don't know how I'd be able to reflash with default firmware when I can't even ping the IP address I'd need to upload to.

I also don't know how to make either of those tools operate on a Mac if, in fact, there is a way to do this.

Is there any way to perhaps reflash via a USB stick?

Is there anything else I'm missing or can try to fix this?