Internet is connected but shows message check your internet connection


Don't be afraid, it is not a big deal.
Please open a terminal and invoke the folloving command:

sudo apt update

You can ignore the lot of output, but look at the last few lines.

Situation 1.

If you can see "Hash Sum Mismatch" in the messages, then you can make some housekeeping by command

sudo rm -rf /var/lib/apt/lists/*

and then repeat

sudo apt update.

Situation 2.

You can see something like this:

"W: Failed to fetch"

Please turn off this ppa-repository in your repo list, then repeat "apt update",

Okay brother, thanks.