Is this a Financial or Non Financial report?

Report Viewers allow drill down for reports built by the report designer.  If there is no task pane nor BI tools tab then you may not be looking at a Designer report hence the question of if it is a financial or non-financial report.  

It's a financial report. And a report manager user can drill down on it.

there is a task pane and BI tools tab for these users that can't drill down

Ah, I see that, within your initial comment, you said the task pane and bi tools are visible, sorry about that, I missed it. 

The drill down should work for the financial designer reports.  Just a reminder, only the Sage Intelligence formulas will work with SI drill down sheets.  Make sure the user is not trying to drill down on an Excel formula.  If the Sage Intelligence formulas are not allowing drill down using the Viewer then there is a problem and I suggest you work with a Sage Support Analyst. https://www.sage.com/en-us/support/   I do not know of an Excel setting for this. 

Segregated this issue to being any formula that has the "GLcurrentperiod" in the formula on the layout generator reports.

Can you click on one of the formulas having the issue and click on the fx icon to the left of the formula and get a screen cap and post it here?

this isn't their install but here's the fx screenshot of what I mean by current period..even the person with report manager rights cannot drill down on anything that has GLCURRENTPERIOD referenced. I opened a case with Sage.

I know what it's suppose to look like. I'm interested if theirs looks like this.

Maybe manually enter in a period # and see if it works.

Yes tried that and same results.