Hi @Alcides_Home_360_Bel Welcome!
n8n 1.87+ added a strict Origin check on the push endpoint (/rest/push), and your log showing Origin, Expected, and Protocol all “undefined” means the Origin header is being stripped before it reaches n8n, so the check rejects the push connection while webhooks, which have no such check, keep working. Env toggles like N8N_DISABLE_ORIGIN_CHECK are widely reported to do nothing once the header is already gone, so the real fix is to inject the Origin header, with the scheme, at the proxy hop closest to n8n.
In your Plesk chain that hop is Apache, not the front nginx. Another Plesk user set Origin only in the nginx directives and still saw “Origin: undefined” because the Apache layer in between drops it. So set it in the Apache directives (Websites & Domains, Apache & nginx Settings, Additional Apache directives) with mod_headers:
See this:
Use https://bot.publicides.com as the value, and add RequestHeader set X-Forwarded-Proto "https" as well, since your log shows Protocol undefined too. Keeping N8N_PUSH_BACKEND=sse is fine; the check applies to SSE and WebSocket alike, so SSE alone does not skip it.
If you would rather not touch Apache, uncheck “Proxy mode” in the same Apache & nginx Settings so nginx proxies straight to the container, then your existing nginx block plus proxy_set_header Origin https://bot.publicides.com; reaches n8n directly.