See https://demo.tify.rocks/demo.html?manifest=https://trep.de.dariah.eu/1.0/iiif/manifests/hdl:21.T11991%2F0000-0011-B8C6-E/manifest.json, is the manifest broken?
https://trep.de.dariah.eu/1.0/iiif/manifests/hdl:21.T11991%2F0000-0011-B8C6-E/manifest.json