nokia 100 sim jumper
In this post you can see nokia 100 insert sim jumpers these jumpers will solve sim problem of nokia 100.
in above diagram you can see a few jumpers that are used to for nokia 100 insert sim problem solution. Check these path with meter and apply jumpers if any of these is missing.
check these resistance and if any of them is missing you can scratch point near by them and apply jumpers there also.