In this quick example I will highlight when you might need to add a line to your .htaccess file regarding max_input_vars.
If you find you can not add fields to your Seblod form or lists then try this:
Open your sites .htaccess file
Add this line of code:
php_value max_input_vars 1000 // change 1000 to whatever you need
Save and close
Check it has taken effect by navigating to Joomla Menu => System => System Information.
Look for Maximum Input Variables
Test your Seblod form or List
If not the solution, drink 4 cups of strong coffee, cry a little, then get googling and post your solution on this site :)