After looking at the sample file, my first guess is that the issue is that the Data tab doesn't have all the dates into the future. Hence, when you open the workbook up on a new day, =TODAY()-2 might not exist, and so it doesn't exist in the InterimData tab which is being charted.

At least that was the issue that I had when I opened your workbook. Excel complained about formula issues on the Parameter sheet and that turned out to be the fact that the dates stopped at the 18 January 2019. Once I realised that and fixed it, the graph looks OK. The Named Range mydatesmy, ='YahooStockQuotes8.xlsm'!mydatesmj, comes out as =INDEX(interimdata!$A:$A,MATCH(Parameters!$E$15,interimdata!$A:$A,0)):INDEX(interimdata!$A:$A,MATCH(Parameters!$E$16,interimdata!$A:$A,0))