An error occurred while connecting to REST API

This is interesting… while preparing the screenshot of debug.log.. when i turned on define( ‘WP_DEBUG’, true );
then the issue is gone…
Do you have any idea? I am re-generating the images.
i will turn off wp_debug after that and will see what will come out.

Same problem (An error occurred while connecting to REST API.) with no errors in debug

@vaikis Open Dev Tools in your browser before starting the image conversion process. What is in the Network tab in Dev Tools when a convert error occurs?

@futureyoon, @vaikis Please download this plugin version and start again images conversion:
https://gbiorczyk.pl/webp-converter-for-media-beta1.zip

What error are you seeing now?

An error occurred while connecting to REST API. Please try again.

{"message":"Request failed with status code 524","name":"Error","stack":"Error: Request failed with status code 524\n at createError (https://****/wp-content/plugins/webp-converter-for-media/assets/build/js/scripts.js?ver=20210923131834.3.2.1:672:15)\n at settle (https://****/wp-content/plugins/webp-converter-for-media/assets/build/js/scripts.js?ver=20210923131834.3.2.1:946:12)\n at XMLHttpRequest.onloadend (https://****/wp-content/plugins/webp-converter-for-media/assets/build/js/scripts.js?ver=20210923131834.3.2.1:74:7)","config":{"url":"https://****/wp-json/webp-converter/v1/paths?_wpnonce=ad61e3f1b6","method":"post","data":{},"headers":{"Accept":"application/json, text/plain, */*"},"transformRequest":[null],"transformResponse":[null],"timeout":0,"xsrfCookieName":"XSRF-TOKEN","xsrfHeaderName":"X-XSRF-TOKEN","maxContentLength":-1,"maxBodyLength":-1,"transitional":{"silentJSONParsing":true,"forcedJSONParsing":true,"clarifyTimeoutError":false}}}

{"data":"\n\n\n\n \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
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\n \n Error\n 524\n
\n Ray ID: **** ?\n 2021-09-23 13:20:16 UTC\n
A timeout occurred
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\n You\n
Browser
\n Working\n
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\n Hamburg\n
Cloudflare
\n Working\n
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\n ****\n
Host
\n Error\n
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What happened?
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The origin web server timed out responding to this request.

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What can I do?
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If you're a visitor of this website:
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Please try again in a few minutes.

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If you're the owner of this website:
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The connection to the origin web server was made, but the origin web server timed out before responding. The likely cause is an overloaded background task, database or application, stressing the resources on your web server. To resolve, please work with your hosting provider or web development team to free up resources for your database or overloaded application. Additional troubleshooting information here.

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\n Cloudflare Ray ID: ****\n ?\n Your IP: ****\n ?\n Performance & security by Cloudflare\n \n

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\n\n\n\n","status":524,"statusText":"","headers":{"cache-control":"private, max-age=0, no-store, no-cache, must-revalidate, post-check=0, pre-check=0","cf-ray":"****-HAM","content-type":"text/html; charset=UTF-8","date":"Thu, 23 Sep 2021 13:20:16 GMT","expires":"Thu, 01 Jan 1970 00:00:01 GMT","referrer-policy":"same-origin","server":"cloudflare","x-frame-options":"SAMEORIGIN"},"config":{"url":"https://****/wp-json/webp-converter/v1/paths?_wpnonce=ad61e3f1b6","method":"post","data":{},"headers":{"Accept":"application/json, text/plain, */*"},"transformRequest":[null],"transformResponse":[null],"timeout":0,"xsrfCookieName":"XSRF-TOKEN","xsrfHeaderName":"X-XSRF-TOKEN","maxContentLength":-1,"maxBodyLength":-1,"transitional":{"silentJSONParsing":true,"forcedJSONParsing":true,"clarifyTimeoutError":false}},"request":{}}

@vaikis It looks like your server starts blocking connections after a while. The plugin has no influence on this.

In this case, convert the images again until you succeed. Do not select “Force convert all images again” option when restarting image conversion. Then only the images that have not been converted before will be converted.