Sorry I'm late to the conversation (~8 months), but I was having these same issues and more, but I just figured out what the problem was for me anyway. It did not appear there had been any real conclusion posted, so that's what I hope this information does.
By the way, I'm not real techie, I just know enough to be dangerous. Some of the posts in this thread were way above my level of understanding. I'm also sorry for the rambling, but I literally just spent two solid days trying to figure this out. Many steps tried and failed. My issues were a combination of this thread and this thread:
https://forum.sharkrf.com/viewtopic.php?p=26592&hilit=openspot+3+manual+upgrade#p26592
To cut to the chase, and maybe save yourself some time, I think the main problem was I subscribed to eero Secure. Once all of the privacy settings were removed and the eero app showed "eero Secure is Inactive," everything seemed to work perfectly. So, if you subscribe to eero Secure or eero Secure +, you really need to make sure those settings are off. Since I did not have eero Secure + I can't speak to what you might need to do to get this to work. I mainly subscribed to eero Secure because my girlfriend has a teenage son and I wanted to limit is ability to access certain sites, etc.
To turn off eero Secure settings you need to access the eero app, select "Discover" then "eero Secure" and make sure the Advanced Security and Ad Blocking are both turned off. You also need to make sure all of the Parental Controls (Content Filters and Block apps) and Advanced (Block & Allow Sites) are all cleared as well.
For reference, as of this post the latest OS3 firmware is V60. I had not used my OS3 for quite some time but suffice it to say that my OS3 firmware was severely outdated. In addition to having outdated OS3 firmware, just about every aspect of my network changed since the last time I used it. New ISP, new router, and new eero Pro 6 mesh router and extension. So where do I begin to troubleshoot? I had hope I would figure it out because although everything was new both ISP and equipment wise, my previous mesh system was still an eero, only it was a 2nd or 3rd generation model, and my OS3 had at one time worked on it.
I was able to follow the directions above (manual upgrade thread) to bring my OS3 to firmware V57, but then that's as far as it would go. Then this thread seemed to be the most relevant. I was really only able to connect to openSPOT3 AP and get as far as connect to my WiFi. I spent way too much time worried about how my new eero Pro 6 was affecting my OS3 to WiFi connection, but I don't think it played any part in my issues. Since I tried SO MANY different things, it might have been an issue, but would have been resolved by going into the eero app, selecting "Settings" then "Troubleshooting" then "My device won't connect," then "My device is 2.4 GHz only" and pausing the 5 GHz just to connect the OS3. The OS3 never had an issue not seeing the available WiFi networks on the eero Pro 6, so I did not have to switch to legacy mode.
First, when I initially tried to connect via sharkrf.link, it was trying to open it via 192.168.11.20, which didn't make any sense. I had already opened my eero app and checked to see what IP was assigned to my OS3 and knew that sharkrf.link should have pointed to 192.168.5.53. I kept getting "This site can't be reached," blah blah blah. So, I manually opened the OS3 using the 192.168.5.53 address.
The OS3 Network settings at the beginning looked something like this:
Mode: DHCP
IP Address: 192.168.99.1
Netmask: 255.255.255.0
Gateway: 192.168.4.1
DNS Server #1: 8.8.8.8
DNS Server #2: 8.8.4.4
With the OS3 / sharkrf.link opened, I looked at the network settings and it showed I was connected to my WiFi, but the internet connection quality said something like "unavailable" or "unknown." On the status page the log was spitting out all similar errors as to what has been described in this thread.
After the eero Secure settings were all disabled I did a network restart on the eero. The next time I opened the sharkrf.link it automatically pointed the OS3 to the correct IP (192.168.5.53) and now the Network settings show the following:
Mode: DHCP
IP Address: 192.168.5.53
Netmask: 255.255.252.0
Gateway: 192.168.4.1
DNS Server #1: 71.10.216.1
DNS Server #2: 71.10.216.2
Everything started looking right on the menu tabs of the OS3 and the "Tools" tab had the gold star next to it indicating there were updates available, like I was used to seeing. The OS3 immediately began downloading and installing the latest callsign database version 202202210817, and firmware version V60.
I set my FCS connector and voila! It works!
