What does 300 dpi mean?
Most professional printed work should use images at approximately 300 dpi at the size they will appear on the page.
Resolution must always be judged at final printed size.
Why web images often fail
A website image may be small and highly compressed. It can look acceptable on a phone while containing nowhere near enough information for print.
Can a small image be enlarged?
Enlarging a small image does not create new detail. It stretches the pixels already there.
Good printing cannot restore detail that is missing from the original photograph.
What should you check?
Check pixel dimensions, resolution, final printed size and whether the image has been enlarged beyond its original size.