Can not visit the CMIS context root, the error is 403.

Check the group/role mapping on the WAS console by following path:

Application servers > BPM.AppCluster.tapallinoneNode01.0 > Installed applications > IBM_BPM_CMIS_BPM.AppCluster > Security role to user/group mapping

And add the users/groups you need to the Default role, then you can visit the /fncmis via the user you filled.