To fix this issue the following can be done:
1. Access K2 Workspace > Security tab > Security node > Workspace Permissions, with an account that has been given specific rights to access the Security Tab.
2. Have this user apply Workspace rights to every required account.
3. Have these users check Workspace to ensure that they have been given sufficient rights to view each Workspace tab.
Confirmation should be made that this fixes the issue. All user accounts applied to the Security section should be able to access each Workspace tab without issue.