I am trying to change a custom field type (Company Logo) to image type, but I received an error message said: "The action was not successful, an unknown error has happened."
Additionally, After checking to debug information you shared with us, I found that you are using outdated Toolset plugins especially Types plugin version. We always recommend running your site with latest stable release plugin version.
*** Please make a FULL BACKUP of your database and website.***
Could you please update ALL Toolset plugins to it's latest official released version. You can download the latest plugin release from your accounts page:
=> https://toolset.com/account/downloads/