The VAT number is not showing up in the VIES database. Does that mean it's not valid?
Although the European VIES database is the main tool used by businesses in the EU to check VAT identification numbers, the information contained in the database is not always up-to-date or complete. Many businesses prefer to use their national portals to obtain more reliable information.
For example, in Germany, businesses check VAT numbers using the "USt-IdNr-Prüfung" service provided by the Federal Central Tax Office of Germany (Bundeszentralamt für Steuern).
However, overall, the VIES database is widely recognized as a reliable source for checking VAT identification numbers in the EU, and businesses are recommended to use it whenever possible.