Well, if you have NOT been using the release lever before removing the CPU from its socket, I suspect that means the last time you put it back into the socket, the lever was already in the locked-down position. This likely to prevent proper contact of CPU pins with the socket contacts. If that is what you have done, you can try to fix this permanently.
NOTE Do it this way ONLY if you did NOT use the release lever last time to remove the CPU, AND had that lever already DOWN and locked before pushing the CPU back into the socket!!!
FIRST, you MAY need to remove the heatsink and fan from the top of the CPU chip in order to be able to rotate the locking bar up to a vertical position. BUT do NOT rotate that bar up yet!! If you have removed the heatsink before and recently, it should not be difficult. But if the heatsink is really stuck to the CPU top, do not force it. If you cannot get things out of the way so the locking bar can rotate up, you may have to quit now before anything else can go wrong.
IF that works and you have free access to the CPU chip, do NOT rotate that locking bar up! Simply remove the CPU from its socket GENTLY as you have been doing WITHOUT raising the lever. Now inspect ALL of the CPU pins VERY carefully in case one or more of them is bent again. Try to ensure they all are straight.
NOW lift the lock lever. Replace the CPU into the socket, and it really should go in easily - almost no effort to get it to drop into the holes. IF you experience any resistance, do not push it it. Pull it back up and check for a crooked pin that is not fitting into an open hole.
Once the CPU is back in its socket easily, THEN rotate the lock lever back down to the lock position. What this does is slide the CPU chip just slightly sideways, and that slides EVERY pin of the CPU into the proper contact down inside the socket.
Finally, if you got this far, replace the heatsink and fan on the CPU top and fasten it down securely according to its instructions. Close up your system and turn on. If this has worked, your system should run properly and keep rinning smoothly, because the CPU chip is making solid contacts and is securely fastened into its socket.