I tried to follow the SAMLtoolkit tutorial and I was able to get it working without any issue. I was able to reproduce your issue in the following two scenarios.
- If you have not first registered the user on the SAMLtoolkit web app which you are trying to logon with you will see this error.
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- If the certificate that you have to download is not the RAW version and the Base 64 version that you download from the Azure AD portal to upload to the SAMLtoolkit portal .
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Hope this helps. Let us know in case if you still see errors and we will e happy to help you further on this .
Thank you .
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