Hi Catymag,
Thank you so much for replying.
Great tool:Jdv, thx for the tip.
I have found no error in the gmapsupp.img via Jdv.
Tried following:
Deleted the gmapsupp.img on the SD card, and used Jdv to install the 2015.20 img. Result: not available in Zumo. (no error indicated by Jdv)
Deleted the gmapsupp.img on the SD card and used Jdv to install a 2014.40 img Result: same: not available in Zumo. (no error indicated by Jdv)
Deleted the gmapsupp.img on the SD card, now installed a segment of 2014.40 via mapsource 6.16.3 Noeman fixed . Zumo recognises it fine !
Deleted the gmapsupp.img on the SD card. now installed same segment of 2015.20 via Basecamp 4.1.2. Noeman fixed.(C:\ProgramData\GARMIN\Maps\City Navigator Europe NT 2015.20.gmap\fixed with Unlock_mapset2.exe) Result: Zumo recognises it fine !
Deleted the gmapsupp.img on the SD card. now installed whole mapset of 2015.20 via Basecamp 4.1.2. Noeman fixed.(C:\ProgramData\GARMIN\Maps\City Navigator Europe NT 2015.20.gmap\fixed with Unlock_mapset2.exe). Result: not available in Zumo. (no error indicated by Jdv)
size: 3.23Gb, 534 mapsegments
Deleted the gmapsupp.img on the SD card. now installed part of mapset of 2015.20 via Basecamp 4.1.2. Noeman fixed.(C:\ProgramData\GARMIN\Maps\City Navigator Europe NT 2015.20.gmap\fixed with Unlock_mapset2.exe). Result: Zumo recognises it fine !

Whole mapset size: 3.23Gb: not recognised
Part of mapset: 850 Mb: recognised.

Is there a 2Gb limit on file size then ? Thought it was 4Gb ?
Software version 4.80.

Thx