I went through this exact thing. I had a trip planned to DLR over Easter weekend. I called DLR initially, asked about refund options. Was told no option existed, but my tickets were good for use through early 2022 - and even afterwards I could exchange there for DLR tickets at the cash value. At that point, I didn't have a new plan hatched, and I didn't know whether I was going to try to get to DLR or WDW. So I got off the phone.
Then, about 2 weeks ago - we hatched a plan to go to WDW at the end of august (which is now looking WAY less likely after seeing the beerflu adjustments the US based Disney Parks will likely make). So I called up WDW and asked them about converting my DLR tickets to WDW. They said no way. The CM was actually quite nasty about it. Was a little weirded out by how short and curt she was with me. I'll chalk it up to Corona stress...but it was still weird.
Then I called back DLR about a week ago and plead my case. All I really wanted was a conversion to WDW tickets - since I'm on the east coast and getting to California is far less likely for me over the next 4-5 years (our easter trip was going to be our first to Cali in several years). The CM put my on hold and came back and said that they couldn't do the conversion because the DLR and WDW systems are simply not connected in any way...but after a little back and forth, a brief pause for the CM to speak with a supervisor and they offered tol refund my tickets back to the original credit card.
Basically, long story short...your only option is to make a plea for a refund on your original tickets. Their front line CMs dont seem equipped to do it without some variety of supervisor override, so you have to be prepared to make a case why you can't get out to Cali any time soon - plan on going to WDW instead and hope they're willing to work with you.