Can you confirm if you are on the free or pro version of the plugin?
A new update was released yesterday updating to version 2.2. For the free version this adds a lot of new features, some of which were only previously available on the Pro version. However, it also requires a database update script to run as the sheet data has to be stored a little differently than it has in the past. It sounds like this may not have run successfully for you. Here are a few things you can try…
1. Go into your admin under Sign-up Sheets > Settings then open the “Advanced” section
2. Click the “Rerun Data Migration” button and wait for it to finish processing. If it display a message that it may have stalled you can try clicking it again as it should try and pick up where it left off.
If it keeps stalling repeatedly, you can try to add a temporary setting to increase the allowed memory used on your site until the process completes. You can do so by adding the code below to your wp-config.php file…
define( ‘WP_MEMORY_LIMIT’, ‘512M’ );
The above code is an example and you can adjust the amount 512M depending on your site and amount of data. If you rerun the migration and notice it gets to a higher percent but still gets stuck, try increasing the limit again. Once the migration is complete you can remove this from your wp-config.php as the migration will only need to be run once.
You can view your current memory limit within the WordPress admin under Tools > Site Health > Info (tab) > Server (accordion heading)
Please let me know if this resolves the issue otherwise we can debug further.