"...when I raise the lever it wont stay in place..."
This sounds to me like the lever is not fully engaging (pressing against) the string? Or is it pressing against the string, but then slipping off again?
If it is a Jordan/Truitt type, the problem may be the BRIDGE PIN is at the wrong height. For these levers to work, the string needs to be held at a precise distance from the neck, so you must have a pin with a groove it it that the string runs over before it goes to the tuning peg. If this pin is "too high" - that is, it holds the string too far away from the neck - these levers will not press against the string. Look on the end of the pin - if it has slots like a screw, it is a threaded pin and you can use a screwdriver to drive it farther into the neck. Most of these pins do not have the slots, and are more like nails. Use a padded hammer or a block of wood between hammer and the pin, and GENTLY tap the pin farther into the neck. It is best to loosen the string and move the string off the bridge pin before making these adjustments.
If you have the Robinson-style lever, it could be the bridge pin is the wrong height as I just described, but it could be either too "high" or too "low". If too low, remove the string & grip the pin with padded pliers to gently pull it farther out from the neck. Or the problem might be the "stop" of the lever (the little bar that stays in one place that the string is pinched against) is set too high or the string is too thick for the particular size of lever. The lever needs to go a little bit PAST where it first makes contact with the string to get it to lock in place. I'm not sure if the position of the stop can be adjusted or not - if not, you may have to get a new lever of the correct size for that string.
If you are worried about breaking the string while working on the lever, it might be best to remove that string, fix the lever, then put the string back. It may take a few days to settle back in to where it does not require frequent re-tuning, but since the string has already been stretched it will settle in more quickly than a brand-new string.
If you have blade-style levers that are not engaging the string, that is a bit more tricky to fix. You MIGHT be able to bend the lever a little bit to the side so it starts to press against the string (although you might break the blade in the attempt), or you might have to remove the blade, fill in the hole in the neck, drill a new mounting hold closer to the string, and re-install the blade. Either way, it could be more challenging than fixing the other types of levers.
If you are not comfortable doing the repairs yourself, hopefully you can find a good harp technician nearby who can fix it.