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All the light switches should have power at all times on one screw. The other screw ahould have power when switched on.   According to your description, they don't.

A triple failure of 3That means whatever is feeding the light switches at once is extremely unlikelynot doing so. If you have receptacles which are also broken, keep following the chain toward source. You may be a broken GFCI or the GFCI itself may not be getting power.

Follow power back toward its source, and you will findIt may be a problem with either the hot or the neutral. If

It is almost assuredly one single problem. Double failures are very unusual.

If necessary, undo wire nuts and measure voltage on each wire.  

All the light switches should have power at all times on one screw. The other screw ahould have power when switched on.  

A triple failure of 3 switches at once is extremely unlikely.

Follow power back toward its source, and you will find a problem with either the hot or the neutral. If necessary, undo wire nuts and measure voltage on each wire.  

All the light switches should have power at all times on one screw. The other screw ahould have power when switched on. According to your description, they don't.

That means whatever is feeding the light switches is not doing so. If you have receptacles which are also broken, keep following the chain toward source. You may be a broken GFCI or the GFCI itself may not be getting power.

It may be a problem with the neutral.

It is almost assuredly one single problem. Double failures are very unusual.

If necessary, undo wire nuts and measure voltage on each wire.

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All the light switches should have power at all times on one screw. The other screw ahould have power when switched on.

A triple failure of 3 switches at once is extremely unlikely.

Follow power back toward its source, and you will find a problem with either the hot or the neutral. If necessary, undo wire nuts and measure voltage on each wire.