@magnusenstrom We’re sorry to hear you are experiencing this issue on your site.
If you are experiencing an issue with the plugin that is preventing you from accessing your wp-admin area on the site, we would recommend to follow the guide here for deactivating the Yoast SEO plugin and then performing a conflict check to determine the source of the issue: https://yoast.com/help/white-screen-when-activating-or-updating-plugin/
Can you please confirm you are using the most recent version of Yoast SEO, version 16.0.2?
Also, if you aren’t able to update in the standard fashion due to the issue, as a workaround, you can also perform a manual update of the plugin. We have instructions on how to upgrade the plugin manually at the following link: https://yoast.com/help/how-can-i-update-my-free-plugin/#ftp. You will need an FTP program such as FileZilla and your FTP details, which can be obtained from your host provider.
Also, can you confirm you are using WordPress 5.7? You can check by clicking on the W in the top left and selecting About. If you need to update, please check with your host provider. Please know that if you are using an older version of WordPress Core you may experience unexpected behavior with Yoast. This guide explains more: https://yoast.com/why-we-dont-support-old-wordpress-versions/