I can't get my garage door to open where my tools are at. It is a
wide 2.5 car door and has 2 large long springs on each side. Yes,
this is the old dangerous kind of spring that loves to snap through
boards & people when they break.

When I look at the door from the outside, there is a visible drop on
the left side which I can plainly see due to a change in paint color
from where I painted it a year back vs. newly uncovered old paint that
was previously hidden. Thus, I know one side has definitely dropped.
I look at the railing/guides and everything tooks fine. Did a cable
slip or is one of the old springs giving out? The springs look okay
and the cable is on both pulley wheels. Beyond that, I don't know
what to look for.

If I lift on the door while someone else actuates the electric door
opener, it will then open with a little help.

Any suggestions on what to check?