It looks like the EOS switch on the right is open. This switch should be adjusted so that it opens only when the flipper is fully extended.

If the switch is indeed closed in the “resting” position, then make sure the contacts are clean.

You could also check to see that the flipper button switch is clean and properly adjusted. A strong flipper requires a low resistance path, so essentially any of these conditions could be the culprit.

If you check all of these things and still have a weak flipper, I would check the condition of the plastic coil sleeve and any play in the linkage. At this point, a bad coil should be ruled out.

In the resting position the EOS switch should be closed as previous poster stated. When you push the plunger into the coil the EOS switch should open when the plunger is just about or fully pushed into the coil. Check the contacts on the EOS and make sure they are clean and touching each other when not activated. Make sure no wires broke off of the coil or EOS.
If the game was playing other than a weak flipper before think of what else you did. Is the score motor in the right position? Try turning the motor 1/3 around and try starting it. If nothing happens rotate 1/3 more and try again. If nothing happens again try resetting the bank manually.