Error installing

Hi, I have tried to add PP to a development site but it seems to be failing. I received the following error and wondered whether you could advise please?

Deprecated: The PSR-0 Requests_... class names in the Request library are deprecated. Switch to the PSR-4 WpOrg\Requests\... class names at your earliest convenience. in /home/ohmobile/public_html/wp-includes/class-requests.php on line 24

Fatal error: Uncaught TypeError: Argument 1 passed to Kibo\PhastPlugins\PhastPress\RequestsHTTPClient::makePhastResponse() must be an instance of Requests_Response, instance of WpOrg\Requests\Response given, called in /home/ohmobile/public_html/wp-content/plugins/phastpress/classes/RequestsHTTPClient.php on line 26 and defined in /home/ohmobile/public_html/wp-content/plugins/phastpress/classes/RequestsHTTPClient.php:29 Stack trace: #0 /home/ohmobile/public_html/wp-content/plugins/phastpress/classes/RequestsHTTPClient.php(26): Kibo\PhastPlugins\PhastPress\RequestsHTTPClient->makePhastResponse(Object(WpOrg\Requests\Response)) #1 /home/ohmobile/public_html/wp-content/plugins/phastpress/sdk/phast.php(9276): Kibo\PhastPlugins\PhastPress\RequestsHTTPClient->post(Object(Kibo\Phast\ValueObjects\URL), ‘\x89PNG\r\n\x1A\n\x00\x00\x00\rIHD…’, Array) #2 /home/ohmobile/public_html/wp-content/plugins/phastpress/sdk/phast.php(2074): Kibo\Phast\Filters\Image\ImageAPIClient\Filter->transformImage(Object(Kibo\Phast\Filters\Image\ImageImpl in /home/ohmobile/public_html/wp-content/plugins/phastpress/classes/RequestsHTTPClient.php on line 29

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Many thanks for your assistance.