I use vB Optimise and get a blank page when I go to threadloom.php.

There is a known issue with vB Optimise where it may not immediately recognize your new Threadloom templates after you install Threadloom.

To fix this, go to Options > DragonByte Tech: vB Optimise - Cache Options, and toggle "Cache Templates" off and then back on again.  This should remove the white page and return your standard template with the Threadloom search box.