compatibility SQL Express VS SQL Standard

Hello.

I am currently using SQL Express 2017. The database has grown so much that I have to switch to the standard version.

I have several programs connected to the SQL server that work on a common database. The specification of one of the programs states that it works only on Microsoft SQL Server Express Edition version 2008/2012/2014/2016 / 2017.Other programs work correctly with the SQL Standard 2017/2019 version. When investing in the program, I would like to buy the latest SQL Standard 2019.

I contacted the producer of the program. Support claims that the program will not work on SQL Standard 2019, that it only works on Server Express Edition 2008/2012/2014/2016/2017.

A few years ago, I was migrating the base of my old sql Express 2008 accounting program to sql express 2017 and everything worked.

I am not an expert in technical matters. But is there a difference between the operation of SQL Express 2017 and SQL Standard 2019? Theoretically, the programs execute SQL commands, which should be backwards compatible.

Can I ask for any information / help ??