Trying to change my flight existing BR award in J fro two to another date

First, tried online, got through to the last page to confirm, and website bombs out.

Then, called the first agent. He said he does not see any I class availability. I told him I can and the website shows it to me. His response, "So, why are you calling me?"

HUACA

This time asked for mileage plus option, and a helpful agent spent about 40 mins with me. I checked AwardNexus and Aeroplan to confirm availability. She could not see it. She went to a customer service supervisor, who tried to do a manual sell, unsuccessfully. Turns out, she says there is no BR availability in I class beyond July of this year.

Facts:
1. Award was booked pre-devaluation
2. Ticketed in Jan, trying to change the date to May next year. Possible issue?

Will try calling again later, but two agents cannot see any I class seems odd.