What game is it? Couple quick things to start with: When you changed the sleeve you might not have got everything lined back up, check to make sure the plunger is running smooth and not binding on anything. Also clean and adjust your EOS switch and flipper button switch.

pinballn00b, you really do need to be a little more specific. What game? There are a few different flipper designs - electrically and mechanically.

Solid state flippers are completely different than direct driven flippers and require different approaches to maintenance and troubleshooting.

hawkeye11 has pointed out the first things you need to look for, ie, go back over the mechanism and check your work. It could be something as simple as not putting the new sleeve in correctly - and yes, there IS a correct and incorrect way to do this.

Rather than give a full blown treatise on flipper designs let's hear specifically what you have so we can diagnose that particular design.

Check to make sure all the bolts are tight. I bet something is getting in the way of a smooth slide. I am thinking this one is mechanical.

This may not be the issue, but I would check the switch in the cabinet that the right flipper button engages. Make sure it looks okay give it a little cleaning on the tips as well and make sure that when you press the flipper button the switch is closing to engage the flipper.

I agree with The_Dude_Abides, try cleaning contacts on the cabinet switch behind the flipper button. Wet a business card with alcohol, close the contacts on it, then drag the card through.

OK MSF uses a direct and solid state control so kind of a hybrid. Definitely do what TDA suggests and check your cabinet fliper switches. They are the direct power control and are tungsten contacts. They do need to be filed once in a blue moon and need to close tightly and squarely to conduct full current. By your description this sounds like the most likley cause of your problem. However...

The other end of that is the end of stroke or EOS switch circuit which needs to be CLOSED at rest and open about 1/16" to 1/8" at full flipper stroke. The points need to be tight when closed and clean. Do not file these, however as they are gold plated, not tungsten. They do not conduct high current but do tell the solid state fliper board to keep pulsing high power until they are open at the end of stroke.

Lastly, for now, check the fuse clips! DE/Sega was known for having cheap, weak fuse clips and without enough tension holding the fuses in the current just can't get through. Trust me, they may look just dandy but pull the hig power fuses and try to wiggle and squeeze the clips. I had one game where 6 clips fell off in my hands when pulling the fuses! Notoriously bad.

Sorry bud, these are not gold plated contacts here. The card swipe is intended only for gold plated low power contacts. This is appropriate for the EOS contatcts, however. For tungsten you need to use a file. Tungsten carries all the current (amps) used to power the flippers in this era of DE/Sega games.

Thanks for that
One other thing I thought of; you say you only changed the sleeve and stop, correct? This doesn't require you to loosen the flipper bat itself but if you had loosened the flipper bat I would ask you to make sure you left a little vertical play in the shaft, about the thickness of two business cards between the playfield bushing and the pawl. A lot of newbies (not you, of course don't leave any gap at all which makes the flipper really tight.

Glad to hear you were able to resolve the problem pretty easily!!