SAML integration works with one instance but not the other

I have two instances of an app, running in Siemens datacenter.  For one, SSO works, but not for the other. The SSO meta data look the same  at …./SSS/metadata, and also all parameters in the SAML runtime configuration, except for the certificate (which is to be expected).   Any indications what the reason for the different behaviour is is highly welcome.  
1 answers

I could resolve the issue, and maybe it is of interest to others:

The problem was not in the runtime configuration of the app. On the IdP side, I types a / at the end of the URL of the app, and consequently the IdP did not accept the request from the app.