SQL Server 2017 introduced a new server-level configuration option called "CLR strict security", and it is enabled by default.

This option requires that all Assemblies, even the SAFE ones, should be signed with a certificate or a strong name key. The Certificate (or the Asymmetric Key) used to do the signing needs to be loaded into the [master] and have a Login created from it. This Login in turn needs to have been granted the UNSAFE ASSEMBLY permission.


You can run the following commands against the SQL server, better if from the Management Studio:

EXEC sp_configure 'show advanced options', 1 
RECONFIGURE; 
EXEC sp_configure 'clr strict security', 0; 
RECONFIGURE;