If you receive this error after having added contents into the GDPR component settings and having saved parameters, it's likely you have exceeded the limit of characters that Joomla! is able to store for parameters of each extension.

CAUTION: IF YOU NEED TO STORE A LONG TEXT FOR COOKIE AND PRIVACY POLICY CONTENTS ENCODED IN UTF-8, USE A SEPARATED JOOMLA ARTICLE INSTEAD OF WRITING IT DIRECTLY INTO THE EDITORS OF THE GDPR COMPONENT

Because of this issue your website may be no more accessible. In such case if you are able to reach the backend, open the Joomla! Global Configuration and disable the GZIP compression and the error reporting:

After that ensure to have cleared the whole Joomla! cache and the website should work again without any error. At this point you are able to open the GDPR component settings and delete the text that is too much long from the related editor field.
If instead the backend of Joomla! is no more accessible as well, to have the website working again open an FTP connection and delete the whole folder of the GDPR system plugin located at: root/plugins/system/gdpr

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