Why Doesn't the Upright Piano Hammer Strike the Strings? How to Fix It yourself

[maxim_tuner]

https://youtu.be/DuQJLpCNLNY
If the upright piano hammer is not striking the strings, the issue may not necessarily be due to the capstan of the key being too low, as this would also require the entire wippen and the jack to be positioned low. However, this does not appear to be the case.
Possible causes include:
The jack flange may be broken.
The pin or screw securing the jack to the wippen may have come loose or fallen out.
The jack flange may have detached from the wippen.
The jack spring may have come loose, be damaged, or be missing.
The spring is responsible for pushing the jack forward.
How to Fix It:
If the pin or screw securing the jack to the wippen is loose or missing, attempt to reinsert the pin into the hole of the jack flange using a screwdriver. If the jack spring is loose, damaged, or missing, gently pull the spring upwards to increase its tension. If it is damaged, replace it with a new one. If the jack flange has detached from the wippen, you will need to remove the action from the piano and unscrew the wippen from the action. Then, use PVA glue to reattach the jack flange into the groove of the wippen. You can either glue the broken flange or replace it with a new one.