Amazon Showcase

I tried to upgrade Amazon Showcase. <the automatic upgrade failed.
I am getting now the error:
Amazon Showcase requires access to hash_hmac()/sha256.

Warning: session_start(): Cannot send session cookie – headers already sent by (output started at /hp/au/ad/he/www/kiminta/wp-content/plugins/amazon-showcase-wordpress-widget/amazonshowcase.php:1333) in /hp/au/ad/he/www/kiminta/wp-content/plugins/wordpress-automatic-upgrade/wordpress-automatic-upgrade.php on line 121

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /hp/au/ad/he/www/kiminta/wp-content/plugins/amazon-showcase-wordpress-widget/amazonshowcase.php:1333) in /hp/au/ad/he/www/kiminta/wp-content/plugins/wordpress-automatic-upgrade/wordpress-automatic-upgrade.php on line 121

Warning: Cannot modify header information – headers already sent by (output started at /hp/au/ad/he/www/kiminta/wp-content/plugins/amazon-showcase-wordpress-widget/amazonshowcase.php:1333) in /hp/au/ad/he/www/kiminta/wp-content/plugins/wp-super-cache/wp-cache-phase2.php on line 48

Thx for every help