I tried to efile 1040NR with tax treaty 20(c), but the return was rejected by taxing authority. The reason is the following. 

This return could not be processed for e-filing due to incorrect or missing information. Review the information that appears on Form 1040NR Schedule OI, Section L. The treaty article must match exactly what the IRS requires. 

My treaty article is 20(c). I also tried many times for efiling, but all failed.  What should I do to solve this problem?    

 Thanks.