I would think I should be able to order past years transcripts with my old address, even if they have not started processing my new tax return. I've received the following message when I put in both addresses;

"Based on the information you provided, we are unable to process your request, please check your records and visit www.irs.com for options available online".

This has been happening since Friday, but Friday was also the first time I attempted to use my old address also. I was able to order transcripts last year.