Re: Window Mobile 10 - Getting error Server Certificate is not Trusted
If windows 10 Mobile does not give you an option to override the warning and proceed then you will need to find out why the certificate is not being trusted. It could be expired; the name of the certificate is not matching the name you are using to access the site or that the chain of trust for the certificate cannot be verified i.e. you do not have the CA and any intermediate certificates installed.
To obtsin a copy of the CA and any intermediate certificates, connect with a browser to the site and export the required certs and the following has steps on installing certs on the Win 10 mobile platform