Hi NNguyen08 and welcome to the community!
Have had similar issues because of the way vCenter now uses the Inventory data (no longer has an Inventory service but the data is being used). In our case we still had plenty of space however one our our ESXi servers wasn't see the correct datastore size. Easiest option is to go to each ESXi server and rescan storage.
You could check the space the ESXi server sees before doing this by running vdf -h to confirm if this is indeed your issue.
Kind regards.