Knowing absolutely nothing about this brand, I would recommend a careful inspection and if you're comfortable disassembly as far as needed using good quality tools. I would look for
1. What should not be there - dirt, debris, foreign objects or rust preventing correct movement
2. What should be there that isn't - missing spring, plunger etc.
3. Damaged parts - broken/bent spring, ear on ejector
4. Incorrectly installed parts - ex. my BIL's rifle would not extract, previous person had the extractor claw rotated 180 deg from functional. I would think you should be able to compare the upper to the lower ejector assembly.
Go slow, try your best to prevent flying parts.
If you are not comfortable with doing this I recommend you take it to someone.