Non-OP players are unable to use shops in spawn protected areas.

If you are using openpac claims you can toggle interaction in the config to allow it.

You just need to open the file in world/serverconfig named openpartiesandclaims-server.toml and modify forcedBlockProtectionExceptionList to include shoppy:shop_block, shoppy:creative_shop_block, shoppy:bartering_station and shoppy:creative_bartering_station

If your using a different claiming system make sure to name it in issue reports as elsewise the developer wont be able to provide support <3