just upgraded my ram and got this messages, whats going on?

[sweet blade]

Can anyone help

[naive cave]

you sure you didn't upgrade the ssd?

[haughty wing]

The message clearly says it....no bootable device found...
Either someone switched to raid or ahci mode....or removed boot options...

[buoyant panther]

You might've accidentally unplugged your boot drive, judging from the message you're getting.

Check if you have your boot drive properly plugged in.