Cannot enable Paypal Standard

[iaadmin]

For some reason my paypal express has stopped appearing as an option in my checkout.

I have double checked the api settings but the Enable this Solution is set to No and i cannot change (greyed out).

Any idea?

thanks

[MagikTejas]

Hi,

You need to check if there is an error in the console related to forms.js while connecting to paypal api credentials? Try clearing the magento cache and browser cache. Make sure the form.js you are having in magento is latest.

[aosdesig]

When clicked paypal pay this is the message you get:

• PayPal gateway has rejected request. Security header is not valid (#10002: Security error).

please help to find the solution.