My organization recently updated from 2.5 to 2.9 and I'm now experiencing issues with a model I built. Specifically the "Geocode Addresses" tool.
In short, what is happening is that after the "Excel to Table" tool runs the Single Line Input value in the geocode tool defaults to 'None' causing the tool to not match any addresses, this in turn causes the dissolve tool to generate an empty output.
This model has been running fine every week for over a year, in fact it ran fine the day just before we updated to 2.9 it seems the changes made between 2.5 and 2.9 have caused this behavior.
What Didn't Work :
Setting the ExcelToTable output as a parameter in the same model as the geocoder did not fix this.
Setting the output as a parameter and setting it as a precondition, and not a direct input, for the Geocoder and pathing the input from the GDB instead also did not fix this issue.
Splitting the model into 2 separate models, with the first model using the Excel To Table tool with the output not being parameter, then running the other portion as a 'nested' model. This caused the Excel To Table output to be deleted after running one time.
What appears to work now:
Having the first model run the Excel to Table tool with the output set as a parameter to stop it from being deleted and then 'nesting' the rest of the process as a second model, preconditioned by the Excel to Table tool.
My best guess as to why this is happening is because the Geocode Addresses tool is being 'staged' (or loaded into memory or whatever) while the Excel To Table tool is still overwriting/creating the input for it, causing it to not find the correct Single Line Input field and defaulting it to none.