Unfortunately, when the quality meter indicates your image is too low in resolution, we cannot print it as a poster.
This often happens if you try to use an image taken from the web. Web images are very poor quality, what looks good on a screen will not look good printed out, even small, let alone as a large poster.
An image needs to have at least 75 dpi (dots per inch) in resolution at the desired print size.
Try finding a higher resolution photo or image to start with. Once you have a high enough resolution image, the order page will allow you to continue and even tell you the largest recommended size for the image.
It’s a common next quesiton for someone to say “my image is too low quality, isn’t there something you can do?” If there was a way to magically enhance your image, we would sure do it. But unfortunately you cannot “create” pixels that don’t exist. That is what causes blurriness. A tiny image can’t be enlarged to giant proportions if it doesn’t have enough pixels to begin with.