Even disabling the plugins did not work.
The good news is I managed to solve the problem: there might have been something wrong with the entry “woocommerce_ppec_paypal_settings” in the Options table: I manually replaced it with an older version and then I could finally change the setting.
Thanks anyway to all of you for the help.
Hello, I tried raising the max_input_vars to 10000 and installing the plugin. It did not help. I also tried disabling some plugins like wordfence.
