Due to the changes in the WordPress 4.4 and the way it handles shortcodes, some of the BBCodes (essentially they are shortcodes) in GD bbPress Toolbox Pro using shorthand method of writing them are no longer working. To fix the issue, you need to:
Update to GD bbPress Toolbox Pro 4.0.5 or newer
Open plugins Tools panel, and there you have WordPress 4.4 Update panel.
Follow instructions and run the update
You are affected mostly for using Quote feature with BBCodes and some other BBCodes. It is advisable to run the update after you update to WordPress 4.4