Last week while coyote hunting I was ejecting a spent case after shooting a coyote when the lever came loose. My gun is a 99EG 250-3000. I haven't taken the stock off yet. What are the possible causes for this problem? The lever seems to have come loose and the bolt can't be open.

Probably the bolt stop screw came loose allowing the lever to open too far and the lever to come out of the track on the bolt.
Take the butt stock off and look for loose parts. Tom

Sounds to me like the projection on the tip of the lever that engages the track in the bolt has broken off.

Those guns are junk, I'll take it for scrap, maybe some parts left that are worth a few bucks.