U2417H, to multiple computers

Hello,

I have a work laptop and personal computer that's I'd like to have both hooked up to a single Dell U2417h monitor.

I have the monitor hooked up from work laptop via DP.

Personal computer only has VGA output, so I have that converted from VGA to mDP in.  However I get the message "No mDP Cable".

Is my issue because I have the single monitor with both DP and mDP?