Can't turn gripshift into top or bottom gears

[scollins]

After finding this site I jumped in for a tuneup on my 6 speed cruiser. Everything was going well until I got to the rear derailleur. I started monkeying with the L and H screws which I don't think needed a lot of adjustment. Video mentioned releasing the tension on the cable. So I turned it clockwise (compressing the spring). I turned it the other way to change to gear 1 and gave it some slack again. After moving back to 6 I can no longer get it to go back to gear 1. It usually only goes to 3 but if I really crank on the cable I can force it into gear 2. But 1 is a no go. I have tried screwing the nut back and forth on the cable but it doesn't help. If its too tight it won't go into 6th gear. I would really appreciate some suggestions.
Thanks.

[TESTUser111]

It sounds like maybe your H and L screws are too tight. Try backing them off, but not too far as they are meant to keep your chain from falling off the high and low sprockets. Then set the cable tension in your highest gear (smallest sprocket) and adjust it as needed as you shift to a lower gear (larger sprocket).

[scollins]

Thanks for the the suggestion. That did the trick.