I created a .dump on Heroku and dowloaded it.
Using pgAdmin4, I created a new table and tried to restore using the Heroku downloaded dump file.
I get the message "pg_restore:[archiver] unsupported version (1.13) in file header.
My pg_restore version is 9.1.13
I found out that pgAdmin4 uses it's own old copy of pg_restore in the application contents. I used my system pg_restore on the command line and it worked.