If you are missing the historical graph, chances are is you're missing a year in the "Use For N Year" column in the soil tests.
Go to the Farm > Soil Tests > (Select your field that has the missing data) > Edit Soil Tests.
Simply add the correct year in the "Use For N Year" column for each result.
Example: Soil test was done in the Fall of 2019, you will want to use 2020.