If you pick your artwork, set the crop, click through, and then see "Upload failed. Please try again.", the transfer from your browser to our storage did not finish. This is not the same as the file being too large, and it is not a fault in your artwork.
What the message actually means
When you upload artwork, the file travels straight from your browser to our storage. It does not pass through the Printumo website on the way. This message appears when that transfer stops part way, or when the file arrives looking different from what your browser said it was sending.
Two things follow from that, and both are worth knowing before you spend an hour on your file.
The file size and the pixel count were already checked the moment you chose the file. If either had been a problem you would have seen a different message naming the limit. So this message is never about a file being too big.
The progress bar can reach the end just before the message appears. That is normal for this error and does not mean the file arrived safely.
First, check whether it saved anyway
Before you upload again, open Products in your Printumo account. If an earlier attempt succeeded, the product is already there as a draft, with your artwork on it. Open it and carry on from where you stopped. There is no need to start again.
What to try, in this order
Click the upload button and try the same file again. A transfer that drops once often goes through on the next attempt.
Turn off any VPN, and come off a work or school network if you are on one. These sit between your browser and our storage and are the most common cause.
Use a wired connection if you have one, or move closer to your router. A weak signal drops a large upload part way.
If the file lives in iCloud Drive, Dropbox, OneDrive, an external drive or a network drive, copy it to your computer's own desktop first and upload it from there.
Try another browser, or open a private window with your extensions switched off.
Try from a different network, for example your phone's hotspot.
What will not help
Re-exporting the artwork at a smaller size. Your file already passed the size check.
Flattening the image or changing it to 8 bit. A JPEG is already flat.
Changing the pixel dimensions. Our limit is 320 megapixels, which is far above any print size we sell.
Still stuck?
Send us a message and tell us the name of the file, roughly when you tried, and whether you are on a home, office or mobile connection. We can look up the attempt at our end and tell you where it stopped.