Hi,

Out of curiousity, are you getting the same error with different form or one specific form? Would it be okay to reinstall the K2 mobile app?

Are you using the android app or the iOS app? 

All forms redirect us to the STS login site since runtime subsite is published with ADFS authentification method on WAP and it seems that only the sts site returns this error:

We are using the android app. We tried to reinstall it but the same error occurs.

Did you get any error if you open the form directly on a mobile browser? Other things to look out for is your SSL certificate. I noticed your sts page is using SSL, so is that SSL certificate valid? Is it a certificate issued from a public CA, or from your internal CA? If the certificate is issued from your internal CA, you will probably have to add that certificate to your mobile device before your device can trust that certificate.

Hello,

no, the form opens normally in the browser - it redirects us to the sts site and than redirects us to back to the form. The cert is valid and issued from our internal CA. I tried to install it on the mobile device after your reply but that didn't help.