Via email and a phone call with Travel Guard over the past 2 days I've learned that, "you do not need to travel by this [voucher] date, however you will need to book a new trip and purchase a subsequent travel insurance policy using the voucher by this date."
I called this World Service Center at 1.800.826.1300 number and also learned the complicated details of applying my voucher(s). They are similar to buying the insurance the first time. I also learned that it can be transferred to a different tour/trip so long as it is done before the trip/tour starts.
My interpretation of that, verified by the person I talked to, is that I can sign up for the Best of Ireland in 14 Days tour for a date in the summer or fall of 2022. And that if one of the 2 formerly listed 14 Day Ireland tours for late September, early October 2021 does happen, and I can get on it, my insurance can be applied to it.
Yes, it would've been much easier if TG had refunded the money and I could start over, but that's not possible.