@bogdy hello, i fiiiinaly figure it out. I was getting the same error, so here is how i fix it.

You have to set primary Key on "id" on both tabels, and both to be auto_increment.
Please check if you have the same data_type on both user_id from notes table and id from users table (for me data_type was set as default : SERIAL - which is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE ) so it was ok.
I had the same error, when i tried to set foreign key from table, so insted, try to set it from SQL QUERY like so : ALTER TABLE myapp.notes ADD FOREIGN KEY (user_id) REFERENCES myapp.users (id);

ps. here was the problem. my tableplus version (i don't know why) didn't put the "id" on the last part ...REFERENCES myapp.users (\here goes "id");
Hope it will help!

Database Tables and Indexes