SOLVED!
It had disappeared from the NA list of installed products for no known reason.
Reinstalled from the archive, re-entered SN, re-scan Kontakt DBF, works now.
Komplete 13UCE,
Win11
I only have one instrument that does this and I can't remember what the solution was.
Session Guitarist - PIcked Acoustic V1.0 10/14/2019
Something about deleting and rebuilding a particular file… IIRC.
(edit) This Was a SAL purchase in 2021.