Importing certificate into Access Manager returns Error importing signed certificate: The full certificate chain is missing.

The user attempted to store a certificate with a certificate chain of one trusted root certificate and 2 intermediates.
The order in which the intermediates where added was wrong and for that reason the error was thrown.

There was confusion on what should be considered  as the first and second intermediate certificate.

Intermediate 1 is the certificate that is signing the entity certificate and should be added as the first intermediate after you have added the trusted root.
Intermediate 2 then should be added as the second intermediate

So the order in which the trusted root certificates and intermediates should be applied in the administration console is as visualized below:
Entity certificate ->  Trusted Root ->  Intermediate 1 - >  Intermediate 2

If you add the trusted root certificate and intermediates in the correct order the import of the signed certificate should work without problems.