Sorry for the confusion. Please note when you have a group account, you can either:
(1) Allocate storage space and download bytes to sub-users, which reduces your main account storage space and download bytes. The benefit is each user gets its own private storage space ("My Storage"), and each user is limited with certain amount of storage space and download bytes. A single user account cannot use all group account storage space and download bytes.
In your case, you allocated too much download bytes to sub-users, leaving your own account with 0 download bytes. You can use the Group Admin feature to re-set the storage space and download bytes.
(2) You can create folders in your own account, then share different folders to different sub-users (with different permissions). When a sub-user logs on his / her account, he/she can access the shared folder in the special virtual folder:
Each user can only access folders shared to him / her. When a sub-user uploads / downloads in a shared folder, he / she uses the folder owner's storage space and download bytes. The benefits of this method are: you can share all your storage space and download bytes with all group users; you can set different permissions to different shared folders (and to different sub-users); all shared folders are visible to the group owners account.
(1) and (2) can be combined for more flexibility. If you want sub-users to only use the shared folders, you can logon as a sub-user (from the Group Admin page), then delete all folders / files in the sub-user account; then logon back as the group owner and reset the sub-user storage and download bytes to 0. This way, the sub-user cannot create folders / files in his / her own account. He / she must use your shared folder in this case.