My iPad says no internet connection but my iPhone is connected.

How is the iPhone connecting to the Internet -- via wide or using its cellular commotion?

Is the iPad a cellular model with a cellular plan?

How are you trying to connect the iPad to the Internet? Do you get any error message?

OK, but could you answer my questions?

Also, when did the problem start? At the same time as your upgrade or some other significant event?

Many reports here of iPads that will not connect to WiFi/Internet after the iPadOS 15 upgrade, no matter what is tried.

Possibly a bug.

Try everything listed below.

After any iOS/iPadOS upgrade/update, you should ALWAYS perform a simple hard reset of your Apple mobile device.

For older iPad models with a Home button, do a simple hard reset of your iPad by holding down both the Home and sleep/wake/power button simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

OR

For much newer, larger screen iPad models, without a Home button, try the new simple hard reset procedure for the new 2018/2020/2021 iPad Pros and the 2020 iPad Air 4 models.

1. Press and release the volume up button.

2. Then immediately press and release the volume down button.

3. Then, press and hold the single sleep/wake/power button You will see the Slide to Power off button, but keep on holding down the power button until you see the Apple logo, then let it go.

Once you have performed all the steps, wait for a few seconds and your 2018 iPad Pro will boot up completely to the iPad Pro’s Lock screen.

Use a VPN? Try, temporarily, disabling the VPN

Then, do a simple reset of the Home wireless/WiFi network MODEM/router box by unplugging from power for 15-20 seconds, or so.

Then re-plug into power and let the MODEM/router box simply re-cycle itself.

Best of Luck to You!