Newsletter form not working when the plugin is active

Hello, my form for the newsletter is not working when the plugin is active. I tried to solve the problem with the newsletter platform but when they realized that I use this plugin, they told me that it is a known issue not only on their platform but for other providers as well.

I searched for a topic and I found one that suggested deleting the plugin and uploading it again from the GitHub. I tried this solution but the problem remains.

Please help me fix it.

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