I have had this issue and boy it's annoying as it makes it hard to focus comfortably. In the end after researching online how to do it I found on ebay a small tool to use for the purpose from a Chinese tool maker which cost $20- $30? and did it myself. I knew my local camera tech did not have the required tool and I did not wish to send it off by mail to an interstate tech who I did not know. It was not technically difficult but it was very fiddly as the slightest turn of the tool made a large difference. Twist the tool then check through the finder then try again usually in the opposite direction was the rule of the day. But after perhaps half an hour of trial and error I nailed it. Even a Leica technician would need good eyesight, steady hands and a calm mind so I can understand why it may be off after a CLA. In your circumstances I say send it back.
PS For those interested in DIY here is the tool. But boy its price has gone up considerably from what I recall. Still - cheaper than paying a technician for a full CLA if that is all that needs adjusting.
and a video showing the method (Note while this shows the technician taking the top cover off this is not necessary if just adjusting vertical alignment) To access the adjustment mechanism it is only necessary to remove the Leica dot on the front of the top plate, behind which the access hole for this purpose resides as you see him do at the end of the video.