S/4 Hana - Output Management via BRF+ Error with KPRO

Hello Experts,

We're upgrading/migrating ECC 6.0 EhP6 to S/4 Hana on-premise 1511 FSP01, and came across the new output management.

We were able to set it up, using our current Smartforms for Invoice (we currently don't use Adobe Forms), and everything seems to work fine, but all outputs get an error because of KPRO.

We believe we configured KPRO as follows:

     1- OAC0 - Created a Content Repository

     2- OACT - Created a Storage Category (assigning the content repository created in step 1)

     3- SICF - Acitvated contentserver service

     4- We have followed all steps in Administration Guide for installation of S/4 Hana on-premise 1511 FSP01 (2.3.4 Setting up SAP S/4HANA attachment services)

After all the configurations, when processing the output in VF31F, we still get the error below:

Any help is very much appreciated!