Have you checked the users POV in Functions->Manage POV? I think in 9.3 and 22.214.171.124 it was called POV Manager. They could have a saved POV that they use to manage C1-C4, if that is set to the top.
Also you may want to just verify security, the generated ICP reports within HFM will kind of bipass security so that if they have access to the partner they can see the data, this doesn't translate in SmartView so you have to actually have access to the entity to see the data. The easiest way to see if it's security or actually showing zeros would be to set the display options to show NoAccess as NoAccess and zeros as Missing to be able to see the differences easily.
I did think it was a security issue at first but the #noaccess doesn't show up. Plus i have more access then everyone and all i see is zeros or #value if i change my display to anything other than #numericzero. I did recreate a small slice of the report as an adhoc report and i was able to pull data. I think the report got corrupted. But its sooooo big to rebuild!
Also, if i do rebuild it as an AdHoc report, will i be able to send it to different users? In the function reports, all you have to do is edit the connection name and that will allow any user to connect privately. Is that the same for Adhoc? Can anyone open it from there pc?
There can be formatting issues when using ad-hoc, I still might take a look at the POV Manager before trying to rebuild the report, as SmartView will default to whatever is in the POV Manager if a dimension is not included in the HSGetValue formula.
As to your question, the answer depends on the version, in some versions (I know 9.3) the sheet level options were not really retained within the worksheet, so things like formatting or suppression can get thrown off if the sheet is shared and everyone does not have the same options selected. If the options are the same, you can change the connection using connection manager in 9.3 and 126.96.36.199 or the Connections dropdown in 188.8.131.52