I have a time SYS module that has the last month of the next years forecast (12/1/2022). When I use the PERIOD() formula and reference this line item it returns nothing. The module where I am referencing does not have time as a dimension. Could this be why?
Yes you are correct. It is because you do not have the time dimension. If you update your formula to select a specific time dimension such as PERIOD('SYS02_Calendar Settings'.'1 + Current Year End Month'[SELECT: TIME.'Jan 21']) then it will return a value.
Do you really need the source line items varied by Time? You are calculating the year-end date but you don't need to vary it by months across the year.
Using year numbers derived from the start date of the Fiscal year can raise problems later on
Having said that, you are on the correct path - just two changes needed and all good:
You have used a summary method for line item "1 + Current Year End Month" to be First Non Blank - which is fine. However, to use it in your destination line item you need to use time aggregation - "Select: Time.'All Periods'"
If Dec 22 does not fall within the model timescale, add a time range to your model which overlaps the potential future years. Note, you don't need to use the time ranges in other places. Please don't add the extra years in the model calendar.
Source Module (Formulas exactly that you have):
Destination Line Item:
PERIOD('SYS01: Time Settings'.'1 + Current Year End Month'[SELECT: TIME.All Periods])