Two Window Sensor issues

Just got started setting up Ring alarm system. I'm having two window sensor issues right now: 1. One sensor will _not_ sync no matter how many times I try again, take out the battery and put it back in, etc. I'm not trying more than one sensor at a time. That's the only advice I get from ther rather sdparse document that came in the box. ideas? 2. These Ring sensors are too big for my casement windows. Ther only way I can get them in is to permanently remove the screens, which isn't a good option. Are there thinner sensors that are compatible? Thanks folks!