If you are going to register a new property in your Google Analytics account and you have selected the normal 'Google Analytics API' or 'Google Analytics Reporting API', it's required that you register your property as a 'Universal Analytics Property', otherwise Google won't make your property available for the API usage.
Google does not support the usage of the normal 'Google Analytics API'and 'Google Analytics Reporting API' for 'Google Analytics 4 property', 'Stream', 'IOS or Android apps' platforms.
When you register a new property in your Google Analytics account for these 2 APIs, you need to:

• Click 'Show advanced options'
• Enabled 'Create a Universal Analytics property'
• Choose to 'Create Google Analytics 4 and a Universal Analytics property' or 'Create a Universal Analytics property only'

If instead you want to register a 'Google Analytics 4 property' domain and use it through the API integration, it's required to select the new 'Google Analytics Data API' and enter the GA4 property ID rather than the domain link:

The GA4 property ID is available in your Google Analytics account visiting the admin area at top right corner: