cannot check in online in Kathmandu

My son and I are in Kathmandu and we have tickets to leave tomorrow (March 21) to fly on China Southern flight 6068 from Kathmandu to Guangzhao and then another flight to San Francisco. I tried to check in online with no success. I type in my passport number and my name and I get an error message. What can I do to check in online? Is there a number that I can call and speak to someone? I called you office in Kathmandu and was switched to this website. Laurence Michalak