Starting a CICS/TS v5.5 region for the first time and it abended U1800 with out any informative message(s).
A system dump, IEF450I CICSSA01 CICSSA01 - ABEND=S000 U1800 REASON=00000000, the Kernel Error Table had an entry for DFHDSDS3 0723.
ACF2/CICS R16.0 CAKSACFI RO96890 06/05/17 14.59
CAIENF R15.0 CARS 2001
The ACF2/CICS module CAKSACFI does not have the required CTS 5.5 support.
RO96890 = CTS 5.4 support
SO04012 = CTS 5.5 support
SO09833 = CTS 5.6 support