installing guest additions

[Sam1951]

I'm trying to install guest additions to a windows 7 ultimate guest. The host system is Linux Mint 22.1. The hardware is Asus Prime B450M AII, Ryzen_5_1400, Nvdia GT 710, 16 Gig Ram.
I think I have the correct version for the VB and Guest additions (7.1.6). The process gets about 2/3 the way through as halts with .... ERROR_AUTHENTICODE_TRUST_NOT-ESTABLISHED (-536870334/0xe0000242). I hope I typed that right, I can't get files in or out of the VM. Maybe I need guest additions to do that?
I have tried {bcdedit /set testsigning on} from an elevated command prompt in the guest. Also running VBoxWindowsAdditions.exe as admin and disabling Windows defender. Same error.
There are some log files but I don't know how to get them out of the guest. I tried setting up a shared folder but that's not working. The bi-directional clipboard also no go. The guest cannot see usb drives, I tried to set that up too.
I'm out of ideas, can anyone help?
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