You are hitting a major roadblock: the well-known free virtual number apps (TextNow, TextMeUp) have been aggressively filtered by most major platforms (Google, Meta, TikTok) because they were widely abused for bulk account creation.
For reliable, free testing where you can read incoming SMS, you should look for open-source or temporary SMS verification services available via web interfaces, not mobile apps. However, if you need a dedicated mobile application, you must switch to low-cost paid services (often specialized VoIP apps) or search the Buy, Sell, Trade (BST) section of the forum for vendors selling high-volume SIM or Mobile Proxy accounts that include valid phone numbers, as these are far less likely to be filtered than general VoIP numbers.