Are you sure your network operator (Three UK?) supports SA mode? Some providers only do NSA, or offer SA only on a subset of their towers. Your QENV servingcell output indicates the module is trying to use SA on the n1 band, but not able to successfully connect there (“LIMSRV” - I see the same when trying to force SA connections to certain bands).
I think Three uses n1, n28, and n78, so you could try temporarily reducing your nr5g_band list to just one of these at a time, though they aren’t deployed everywhere, and n78 tends to have very short range. Three likes to do DSS / Dynamic Spectrum Sharing also, where 4G and 5G intermingle on the same bands, which may also be incompatible with SA mode.