Really no idea what you are doing wrong. You seem to be on Windows, and I can assure you that TAChart is running fine out of the box because I do most of the development on Windows.
You still seem to have a mixup of versions. What was the version from which you upgraded? Did you install over the old version? Did you allow the installer to erase the old user profile? Normally these are no issues, but if you come from a very old version, nobody knows what happens if the new installation mixes with the old one.
Before trying a new installation you should do a clean re-build of the IDE. Select menu "Tools" > "Configure build Lazarus". In the box "Clean up" select the option "Clean all" (and maybe "Switch after building to automatically") - see screenshot. Click "Build". Now Lazarus erases all compiled units and recompiles all packages and the IDE - this may take some time, please be patient. At the end, Lazarus restarts the new IDE.
If this compilation process aborts, something is wrong with your installation. I guess the shortest way would be to install Lazarus again. Unistall the older version first, erase the old installation directory if anything is left afterwards. Erase your user profile in c:\users\<your name>\appdata\local\lazarus. Note that the name of the installation folder must not contain spaces (i.e. "C:\program files" is not good) because some tools used by Lazarus don't like this. Instead, install to c:\lazarus (if you have write access to c:), or to d:\lazarus (if you have a second drive), or to your user data area (c:\users\<your name>).
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