I use T3 Framework and install SP Page builder buy I can't save page and error text
"The most recent request was denied because it had an invalid security token. Please refersh the page and try again."
My server provider has informed that log error
"[Mon Jan 25 16:03:01.322493 2021] [php7:warn] [pid 7318] [client 171.97.99.137:0] PHP Warning: Use of undefined constant discountAmount - assumed 'discountAmount' (this will throw an Error in a future version of PHP) in /home/raminthr/domains/mydomain.com/public_html/templates/t3_bs3_blank2/html/com_virtuemart/sublayouts/products_horizon.php on line 102, referer: http://mydomain.com/index.php"
however, I can save short page normaly but long page can't save.
How to fix it?