Sometimes a disposable vape stops firing because it's genuinely defective. This happens with any product, and it's not your fault.

• If the device overheats excessively, stop using it immediately and dispose of it safely.
• If you see any leakage from the battery area, that's a serious safety risk. Don't use it.
• If the device tastes burnt, the coil is fried. Replace it.

These are valid reasons to be annoyed, and you're right to expect better. But the fix is replacing the unit, not trying to repair it yourself.