I'm not having those problems. For Ground Adv make sure your labels have dark enough ink, no gaps in the printing, and that they're secured to a flat, scannable surface on the package. For ESE, see below.
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eBay Standard Envelope (ESE) is a metered machinable letter mail shipment so it does not receive traditional tracking scans. The clerk at the PO counter cannot scan it and you can't track it on the USPS website. The envelopes are scanned by sorting machinery at distribution centers along the way and tracking will appear on eBay.
Common reasons ESE labels don't get scanned include:
- Overpacking. Envelopes are too stiff. It's not recommended to use trading card top loaders or cardboard mailers. Envelope should be flexible enough to wrap around a water bottle.
- Using ineligible packing material such as a bubble envelope.
- Placement of label. Label should be placed in the upper right corner with approx 1/8"-1/4" clearance from edges, just like you'd position a postage stamp. If it's placed too far from the corner (like in the middle of a long envelope) the machinery may not scan it.
- Securing items like coins in the center of the envelope. The center of the envelope needs to be the most flexible part. It's better to secure single items off to the right (opposite side of label barcode).
- Printer ink is not dark enough, or label color is too bright (stick to white labels if you can).
- Regional issues with sorting machines, volume processing, picky USPS employees, etc.
With ESE, a 'delivered' scan generally occurs at the last sort facility before it gets to the buyer; sometimes the buyer will receive their order a few days after the delivered scan.
If a buyer files a not received claim, you do have insurance coverage and the claims process is outlined on this page: https://www.ebay.com/help/selling/shipping-items/setting-shipping-options/ebay-standard-envelope?id=...
