"cryptsetup failed" Please unlock sda5_crypt" Huh?

Support & Help Requests
#1

First, I’m not a Linux/Ubuntu/Mate aficionado so please don’t wail on me for not being like you are today, because I’m like you when you first got started.

I HAD Ubuntu 16.04 working fine.
I didn’t/don’t care about any data on it.
I ‘‘upgraded’’ to Mate by installing via DVD.
After install completed, I removed the DVD as instructed and clicked to “Restart”
Error “NO OPERATING SYSTEM FOUND”

I did NOT choose to run from the DVD, but clicked to Install it.

I re-inserted the DVD and let it boot again.

Now I get the ““cryptsetup failed” Please unlock sda5_crypt” which refuses to accept the only password I was required to enter, and selected NO login.

I can’t start the comp without he DVD, and can’t load Mate because it wants a unknown password to a something I’ve no idea what it is; the sda5_crypt is alien as is the password.

How can I reformat and retry, again, or at least get the comp back with a O/S?

Thanks for being nice,
S
My box:
Toshiba Aspire Satellite A660
iNtel I5
and that’s all I know because there is no O/S now to look up details.

#2

My suggestion is that you use the live dvd this time to run an instance of Ubuntu MATE. As the computer starts, I usually have to press F12 to get a “one-time” boot option menu. Select the CD or DVD choice and “Try Ubuntu MATE without installing”.

From the title of this thread, it appears that you tried to install UM Mate with some sort of encryption. Please don’t do this. Use the “Erase disk and install Ubuntu MATE” option. This should get your computer back operating with a usable operating system.

If there are any questions, any at all, please reply. Good luck @Internaut

Edit: By the way, https://askubuntu.com/questions/587934/ubuntu-14-04-2-cryptsetup-failed-on-boot makes for interesting reading on this topic.