

& provide a link so I can take a closer look. Better yet, if it isn't confidential data, save a copy of the file on OneDrive, Dropbox, etc. If you still have a problem it might help to have a screen shot. Please understand that I'm kinda shooting in the dark here because I have no idea what Chart type you're using & I know nothing about the data or its fluctuations.

Also, make sure you're saving in the.xlsx format as opposed to the older.xls file type.

See if it helps to right-click the line, go into Format Trendline, then reselect Logarithmic. Sometime the choosing a different type can be a tiny bit stubborn, especially if changing an existing trendline. When I add a trendline, it seems to have no relationship to the selected data series.
