creating a working paypal express checkout button for rest api

just paste the api id and secret into the website code via the cpanel and i got this error Paypal ErrorPayPal\Exception\PayPalInvalidCredentialException Object ( [message:protected] => Credential not found for default user. Please make sure your configuration/APIContext has credential information [string:Exception:private] => [code:protected] => 0 [file:protected] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Core/[login to view URL] [line:protected] => 154 [trace:Exception:private] => Array ( [0] => Array ( [file] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Rest/[login to view URL] [line] => 56 [function] => getCredentialObject [class] => PayPal\Core\PayPalCredentialManager [type] => -> [args] => Array ( ) ) [1] => Array ( [file] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Handler/[login to view URL] [line] => 51 [function] => getCredential [class] => PayPal\Rest\ApiContext [type] => -> [args] => Array ( ) ) [2] => Array ( [file] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Transport/[login to view URL] [line] => 71 [function] => handle [class] => PayPal\Handler\RestHandler [type] => -> [args] => Array ( [0] => PayPal\Core\PayPalHttpConfig Object ( [headers:PayPal\Core\PayPalHttpConfig:private] => Array ( [Content-Type] => application/json ) [curlOptions:PayPal\Core\PayPalHttpConfig:private] => Array ( [32] => 1 [78] => 10 [19913] => 1 [13] => 60 [10018] => PayPal-PHP-SDK [10023] => Array ( ) [81] => 2 [64] => 1 [10083] => TLSv1 ) [url:PayPal\Core\PayPalHttpConfig:private] => [method:PayPal\Core\PayPalHttpConfig:private] => POST [retryCount:PayPal\Core\PayPalHttpConfig:private] => 0 ) [1] => {"intent":"sale","payer":{"payment_method":"paypal"},"redirect_urls":{"return_url":"[login to view URL]","cancel_url":"[login to view URL]"},"transactions":[{"amount":{"currency":"USD","total":"5"},"item_list":{"items":[{"name":"1 Placement matches","currency":"USD","quantity":"1","price":"5"}]},"description":"Unranked Boosting","invoice_number":"569ff060c387b"}]} [2] => Array ( [path] => /v1/payments/payment [apiContext] => PayPal\Rest\ApiContext Object ( [requestId:PayPal\Rest\ApiContext:private] => [credential:PayPal\Rest\ApiContext:private] => ) ) ) ) [3] => Array ( [file] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Common/[login to view URL] [line] => 102 [function] => execute [class] => PayPal\Transport\PayPalRestCall [type] => -> [args] => Array ( [0] => Array ( [0] => PayPal\Handler\RestHandler ) [1] => /v1/payments/payment [2] => POST [3] => {"intent":"sale","payer":{"payment_method":"paypal"},"redirect_urls":{"return_url":"[login to view URL]","cancel_url":"[login to view URL]"},"transactions":[{"amount":{"currency":"USD","total":"5"},"item_list":{"items":[{"name":"1 Placement matches","currency":"USD","quantity":"1","price":"5"}]},"description":"Unranked Boosting","invoice_number":"569ff060c387b"}]} [4] => ) ) [4] => Array ( [file] => /home/cheaxqco/public_html/checkout/PayPal-PHP-SDK/paypal/rest-api-sdk-php/lib/PayPal/Api/[login to view URL] [line] => 579 [function] => executeCall [class] => PayPal\Common\PayPalResourceModel [type] => :: [args] => Array ( [0] => /v1/payments/payment [1] => POST [2] => {"intent":"sale","payer":{"payment_method":"paypal"},"redirect_urls":