There is already an object named 'TaxRate' in the database. Can't install plug in (version 3.9)

I discovered this error when trying to determine why the tax rates were not working. The taxrate plugin was installed in 3.8, but after updating, became uninstalled.
When trying to install it again from the plugins menu, I get the "There is already an object named 'TaxRate' in the database." message. (NOTE: I have the same problem with the flat rate shipping).

The plug-in is in the correct folder.

Group: Tax providers
FriendlyName: Manual (Fixed or By Country/State/Zip)
SystemName: Tax.FixedOrByCountryStateZip
Version: 1.00
SupportedVersions: 3.90
Author: nopCommerce team
DisplayOrder: 1
FileName: Nop.Plugin.Tax.FixedOrByCountryStateZip.dll
Description: This plugin allow to configure fix tax rates or tax rates by coutries, states and zip codes

I've rebuilt the solution and  verified the build, so I'm at a loss as what to do (or where in the database this info is stored)
Help!

I presume you haven't seen the "Readme.txt" file durign the upgrade:

8. Combine "Nop.Plugin.Tax.CountryStateZip" and "Nop.Plugin.Tax.FixedRate" plugins into single one. Upgrade instructions: do not forget to manually delete "/Plugins/Tax.FixedRate" and "/Plugins/Tax.CountryStateZip" directories (they are not used anymore) and replace the plugin «Tax.Fixed» or «Tax.CountryStateZip» by the plugin «Tax.FixedOrByCountryStateZip» in the App_Data/InstalledPlugins.txt file.

I got it. A simple readme I ignored. But someone had to be the idiot today, and that was me! :)

I followed the directions from the readme and I still have no tax provider.

help!