The Structured Data Testing Tool (SDTT) from Google was deprecated some months ago. The SDTT moved from Google to Schema.org with a new name: Schema Markup Validator (SMV). It is now available under the URL https://validator.schema.org/ as a preview.
[x] The validation of schema markup in the the Admin Panel is moved from SDTT to SMV.
The Structured Data Testing Tool (SDTT) from Google was deprecated some months ago. The SDTT moved from Google to Schema.org with a new name: Schema Markup Validator (SMV). It is now available under the URL https://validator.schema.org/ as a preview.
See also: http://blog.schema.org/2021/05/announcing-schema-markup-validator.html