Hm I compared the DNS via https://toolbox.googleapps.com/apps/dig/#TXT/ and the mail-tester link with the extracted signature and there something different:
DNS:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAo0n+CwNRNQQYPu3rdqicjWDibSQEs8ywOQeWBj3+2Ck/k7FFQvzv5JilPEe6k9d1jMGKA0JV3LgHgAC/qVJaTip0P/0o9puWrZ8RJMWLK6hMbh32YOlnuc5Wpvb8F6tooPv/D4Orbbwr4cAcqXYIaczhGkuiv1VDuoPkY4WTc8qK6r2DGMHuGxV,ZCjN+n3CuwzimASk8X1BhprOq4qbhFntlFi3/iRg9LMF64pboy429Wj4YymVtsVZlVUia6Z3vKdycO0BbUFxjFcSyIE/0VvOXJqpyiZ3TviW/0DY9Kjh1hrkuFYwAviwJjOhVlmzAdIRaSQoLxXgjkXphHQ0qQwIDAQAB
mail-tester:
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAo0n+CwNRNQQYPu3rdqicjWDibSQEs8ywOQeWBj3+2Ck/k7FFQvzv5JilPEe6k9d1jMGKA0JV3LgHgAC/qVJaTip0P/0o9puWrZ8RJMWLK6hMbh32YOlnuc5Wpvb8F6tooPv/D4Orbbwr4cAcqXYIaczhGkuiv1VDuoPkY4WTc8qK6r2DGMHuGxVZCjN+n3CuwzimASk8X1BhprOq4qbhFntlFi3/iRg9LMF64pboy429Wj4YymVtsVZlVUia6Z3vKdycO0BbUFxjFcSyIE/0VvOXJqpyiZ3TviW/0DY9Kjh1hrkuFYwAviwJjOhVlmzAdIRaSQoLxXgjkXphHQ0qQwIDAQAB
There’s a comma in the DNS but not in the extracted signature. Can you double check it?