I created the .dmg s using Disk Utility . Strange also that on the new Mac there are only AES 128 encrypting ,on the Old Mac I can still use AES 256 encryption .I have a mobile internet ,which I deem it most bad ewer 5G mobile internet ,I have a router of course ,it is a mobile router. Big companies has this mobile internet - and in this house there are no FIBRE internet - which is indeed most strange too .
I can open all the .dmg files on my new Mac ,but not on the old one . Also the old Mac has a better passwords Generator and it generates short passwords which I deem somewhat risky . - a lots of things is strange .
In Finder double clicking on the file - then it says : The disc image could not be opened.Could not load file or wrong format on UDIF - image .
Klicking on the Desktop ,it says that ,Disc image cannot be opened as Original is not found , as I remember.