OP, by any chance does your router and printer have WPS buttons, if so, turn BOTH off, then turn on the router and press the WPS button, turn on the printer and press the WPS button with any luck the two will find each other and you will be able to print. NOTE: you may need to tell your printer software that you are using WPS as the connection, I use this for 2 Brother printers and works very well.

Canon Pixma TS 9521C
HP Laptop

The USB port should be next to the ethernet port and above the power cord connection.

Did more searching and it looks like a typical, square printer-side USB connector. I don't believe I have a spare of those though if they are no longer supplied with the printer then I wish I had kept one.

Canon PIXMA TS9521C | Canon U.S.A., Inc.

Hi-Speed USB
Ethernet
PictBridge (LAN/Wireless LAN) 14
Wi-Fi® (802.11b/g/n wireless networking, 2.4 GHz) 2
Memory Card Slot 5
Bluetooth 4.0 LE (Low Energy) 8

Just ordered a USB cord...thank you everyone!!!!

From the specs above, it looks like the printer will only do 2.4ghz wifi. Most routers will now do both 2.4 and 5ghz but the 2.4 may be turned off by default check the settings on the router to verify. You will need the printer to connect to the 2.4 network.

I have T-Mobile home internet and I name the 5gh and 2gh WiFi with different names so I can see how they are connected and be sure that when I'm setting up things I know that I'm using the desired WiFi band.

I have a separate modem and router. Mine was not working one day so I tried to connect again. Of course you connect to the router right? Apparently not. After trying multiple times and becoming frustrated I was ready to throw the printer out the window. I don’t know what made me do it but I put the modem’s password in the printer and lo and behold it worked. Good luck

Network Speed
 

A lot of older devices work at 2.4 GHz (GigaHz). Your router is able to run 2 channels. Most cable companies set them up for a single channel at 5 Giga HZ to increase bandwidth and speed. Ask your provider to set it up for both speeds and connect your printer to the 2.4Ghz. Should I use 2.4 GHz or 5 GHz WiFi? | CenturyLink

I had the same problem. Geek Squad came in and the only solution was to hard wire the printer via USB cable. Works great now. Better than wireless.

Disable S Mode to allow the installation of any apps you want. Microsoft does not have the app you need.

Try this. Open the Tmobile app. Go to Network-select the WIFI name-scroll down to Advanced settings. The second drop down should be WPA Version and is probably defaulted to WPA2/WPA3. Instead select WPA/WPA2. Retry connecting the printer on WIFI.

Not a waste of time at all. Good to see that I'm not the only one with the problem. Interesting to learn what has worked (or not) for others.

I haven't tried it but I'll bet calling Cannon would be the waste of time. Search for a number, wait on hold, get directed to the wrong sales staff, and then finally get tech support to tell you to install the latest drivers. Call back again when that doesn't help and get told that the problem must be with the modem. Waste of time - better to ask if anyone else has found a solution to the problem.

Yes, I was able to fix this problem with my new T-Mobile router recently and connect my older HP printer. The issue is the printer only accepts an older password format for the internet password. Download the T-Mobile internet app and change the password format option, there is a list. You may need to have the printer on so the app will see it. I forget which one worked, but there are maybe 3 choices, maybe something like n or n2? When you get the right one the printer will be able to log in because it can see the password. My printer gets connected by manually entering the login on a menu physically on the printer itself.

YES, this is what worked for me, only my original post was very general because it was a few months ago. Great info!