It could possibly be a server issue.
When starting a new server, there is a property in server.properties called spawn-protection. On a standard server, the only users that can modify blocks within this region are ops.
You can make yourself an op by running this command on the server op playername. Alternatively, you can edit the ops.txt file directly and add your username to the list.
Refer to this previous [Question][1] [1]: https://gaming.stackexchange.com/questions/132144/why-dont-mined-blocks-show-up-in-my-inventory-on-my-spigot-serverQuestion