Problem with Date column and One Drive source.

Hello,

I'm new to Power BI and I'm facing quite a few challenges.

1. I created a report on my PowerBI Desktop application connecting it to a file stored in my One Drive Business ( via navigating to the folder synced with my PC and not via URL). I did not think of my requirement then, but I need the report to be consumed by someone else who can update the One Drive Sheet that I will share with them. PBI Service won't allow me to refresh the data source, it's asking to get a gateway, which is a possible solution but not idle. Is there a way to fix my current source to One Drive Source?

2. Since it was not a big report, I decided that I will first create a data set in PBI Service using my One Drive file and then connect to this data set using PBI Desktop. The problem is, after connecting, PBI Desktop doesn't show the DATA or Table tab. So I'm not able to edit anything.
Secondly, I used a DAX: 

Prior Month Total = CALCULATE([AmountSUM], PREVIOUSMONTH(Table1[Month]))

and it worked fine in my original report, but in this report, I'm getting an error that it's not in DATE format. This could be because, in my original report, data column was single column, but for some reason when I connected to PBI Service Dataset that I created, the date column split into Year, Month and Day and they don't have any symbol against them so I assume it's text format. I'm not able to change the format form modelling tab as it's greyed out.

 

My dates column just has two dates 2/1/2019 for 38 rows and 3/1/2019 for 40 rows. Basically I just have data for monthly analysis and no specific dates are given.

Let me know if more information is needed from me.