Dear @carolinabagulho
That could be the issue, are you able to log into your 'Webhost' and update this? It cannot be done through Lay Theme.
The Server or Host who controls your domain should have a 'control panel'
"Please make sure you are using a PHP version greater than 5.2. On most webhosts you can set the php version in the webhost control panel. Also make sure you are using the latest Lay Theme version."
From: https://laytheme.com/troubleshooting.html#json-invalidated
If you go into 'tools - Site Health' in your admin bar what PHP does it say?
Screen Shot 2020-12-11 at 12.05.16 AM.png
https://kinsta.com/knowledgebase/how-to-update-php-in-wordpress/
Best wishes
Richard