Two things usually explain it.
1. The plan started earlier than you think
Days count from the first time the eSIM connected to a network it covers, not from when you installed it or landed. A stop-over in a covered country can start it. More.
2. The data ran out
On a data pack, the eSIM stops when the data is used up, even with days left. My eSIMs then shows Data used up. Top up to carry on with the same eSIM.
Check it
My eSIMs shows days left and data used. Still doesn't add up? Talk to a human with your order number. We'll check the activation time and usage with the network.