Some weirdness in Amtrak.com for Maple Leaf, now that it is reservable. In all the following, note that CBN is a placeholder station representing the border (Canadian Border Niagara).
1. Coach is fine, no big issues booking TWO-NYP
2. On the simplified "one-way" interface, Business only shows available TWO-CBN on 7097 for an additional dollar, but it is unavailable CBN-NYP on 64.
3. Using a single segment on Multi-City, it shows Business available on 7097 TWO-CBN, and as "sold out" on 64 CBN-NYP.
4. On all through TWO-NYP single segment, both simplified one-way and Multi-City, Senior fares are available.
5. Business class is available on the same 64 departure NFL-NYP on an independent booking.
6. Using Muti-City to book a same day, two segment TWO-NFL and NFL-NYP on 7097 and 64 is bookable. TWO-NFL shows as multiple trains, 7097 TWO-CBN and 64 CBN-NFL and then the second segment NFL-NYP. Note CBN-NFL actually consists of walking out of the Customs area into the public area of the station.
6. Using two segment Multi-City, Business Class is available TWO-CBN on 7097, but sold out on "64" CBN-NFL (walking out of Customs). It shows available on 64 NFL-NYP.
7. Senior fares are unavailable on any two segment Multi-City.
When setting up the cross border operation of the Maple Leaf in Arrow, it appears they did not set up Business Class on phantom 64 CBN-NFL. That appears to be blocking any booking of Business Class past the border from Canadian points. Note that booking Business Class TWO-NYP had never been an issue prior to the COVID suspension, even if you weren't seated there TWO-NFL (I always was).