Followed all your steps, uninstalled from Extension Manager, checked for the plug-ins, they were no longer there, checked with Filezilla to see if the directories were removed, emptied the {prefix}_artiofusioncharts table so all my old charts were gone. Then reinstalled the 'User' version.
Next I created a new chart and the problem persists. Like previously no problems with the Pie 2D charts, but the Bar 2D charts give me problems. Unfortunately, my host is doing maintenance, so I can't access the MySQL database currently to check the XML code in the chart records, but some older Bar 2D charts show no problem with labels, but all persist in the 'Free' look, not the enhanced look of the 'User' or commercial version.
On this page
ppbm7.com/index.php/final-results?showall=&start=2 you will see the Column 2D chart that still lacks the 'enhanced' look, but on this page
ppbm7.com/index.php/the-price-tag you will see the 'enhanced' look in the Pie 2D charts.
Note that the first chart is using a real time MySQL link to update the data dynamically, something technically impossible with the 'Free' version.