tried all of these and nothing worked, found final solution that works rails 7+
go to `config/environments/production.rb`

find this line that is commented out (aprox line 20ish) and remove the comment `config.require_master_key = true`
next go to your console and run this command to get the .gitignored master.key value to populate into the heroku env vars

``` heroku config:set RAILS_MASTER_KEY=`cat config/master.key`
# yes thats a tilda, make sure it remains a tilda so that the shell command executes ```
Either I missed it, or its just not super clear in the heroku/rails docs but hope this helps someone from searching in circles

tried all of these and nothing worked, found final solution that works rails 7+
go to `config/environments/production.rb`

find this line that is commented out (aprox line 20ish) and remove the comment `config.require_master_key = true`
next go to your console and run this command to get the .gitignored master.key value to populate into the heroku env vars

``` heroku config:set RAILS_MASTER_KEY=`cat config/master.key`
# yes thats a tilda, make sure it remains a tilda so that the shell command executes ```
Either I missed it, or its just not super clear in the heroku/rails docs but hope this helps someone from searching in circles