Both my wife and I bought a Solterra in the US. I can tell you all of these benefits were received in an email from Subaru of America directly.
I bought mine in late December. I actually received my Just DRIVE promotion code email the day before my scheduled pickup, but it says it was only good for two years instead of the three that were promised. I did not receive the charging credit email at that time. I reached out to Subaru support to complain about both these things and they took a very long time to get back to me. They did early this month and I sent them some email screenshots and have not heard back again since. I DID eventually receive my charging credit email earlier this week and it is added to my EVgo account with no issue now. Not sure if the customer support did anything or if it just took a while.
My wife picked up her Solterra this past weekend. She got BOTH offer emails the very next day. Her Just DRIVE was also only 2 years, but I am waiting to see if I get a resolution to my rental promo before complaining about hers. I was able to apply her charging credit to the same EVgo account, so I have a combined credit of $800 for charging.
So I believe the dealer is correct. They register the purchase with Subaru, and they are supposed to send you your promotions. You need to bug Subaru again.