Yes, Instagram allows up to 10 photos or videos in a single post (carousel). If you can't post 20 photos, it's because you're exceeding this 10-photo limit. To share more, you can:
Yes, Instagram limits carousel posts to 10 photos/videos per post.
That’s why you can’t add 20 photos in a single post.
To share more, split them into multiple posts or Instagram Stories.
Instagram limits a single post (carousel) to a maximum of 10 photos or videos, so you can’t post 20 at once. If you want to share more, you’ll need to create multiple posts or use Instagram Stories instead.
Instagram currently allows up to 10 photos or videos in a single carousel post. That’s why you can’t post 20 at once you’ll need to split them into two separate posts.