Imo db values still exist from the prior install including the settings for the theme select block. This block changes the theme of the forum but does not actually adjust the overall theme setting from your admin panel. If the permanent setting was not previously opted the setting will only effect the current page where the block resides.
The theme it is attempting to select no longer exists, hence no css values which gives you a white background and the whole text display will appear on the left side of the screen.
On the home page, scroll down to the theme select, opt default curve theme & press CHANGE.