cannot get the multisite to work

I attempted to install multisite but nothing come on (no menu to add site..)

What version of WordPress are you using?
What did your attempts consist of?
Were you using the instructions from the Codex?
The network admin link has moved with different versions of WordPress, details here: https://codex.www.ads-software.com/Multisite_Network_Administration#Network_Admin_Link_Location

Do this: https://wpmututorials.com/how-to/how-to-disable-multisite/

I got to the point where this error message is shown.

https://lh3.googleusercontent.com/-AJ5GI-3YngM/UDEr3P_tfnI/AAAAAAAAPzU/K2PTvossvmo/s400/cap.png

I tried to clear the table as the wpmututorials.com suggests. But when it comes to this stage the same error message is shown.

Did you also reset the wp-config and .htaccess?

If you think you did it all, just go ahead with the rest of the install.

I have modified wp-config and .htaccess as they suggested.

what do you mean by “reset”?

Modifying the wp-config (i.e. returning it to it’s natural pre-Multisite state).

I tried to clear the table as the wpmututorials.com suggests.

Since you say ‘tried’ here, can you elaborate?