OnlyOffice integration with NextCloud fails when trying to save settings

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I have NextCloud, OnlyOffice Document Server , and the NextCloud OnlyOffice integration app version 7.1.2 installed via docker (community app store) on my unraid server version 6.9.2. Have https certificates and proxy handled by Nginx Proxy Manager docker app.
Urls are and

Certs are for different for each url and generated by letsencript in NPM. I added the certs from NPM to the created certs directory in the Data folder in the OO docker filesystem.
NextCloud functions fine except for when I try to add the url for my onlyoffice install. I am able to get to each url via chrome browser. I can see the welcome page for OO and also see true when I manually type in the ‘healthcheck’ url for OO.
When I try to save the url in nextcloud on the integration page, it spins for a while and eventually throws this error in the log file:

[2021-10-26T21:26:42.179] [ERROR] nodeJS - error downloadFile:url=;attempt=1;code:ETIMEDOUT;connect:true;(id=conv_check_1111644120_docx)
    at Timeout.<anonymous> (/snapshot/server/build/server/Common/node_modules/request/request.js:848:19)
    at ontimeout (timers.js:436:11)
    at tryOnTimeout (timers.js:300:5)
    at listOnTimeout (timers.js:263:5)
    at Timer.processTimers (timers.js:223:10)

Also I can point to the demo onlyoffice server and it works fine

There seems to be a connectivity issue between your Document Server and Nextcloud.
Please enter the Document Server container with docker exec -it [container_id] bash and execute wget https://your_nextcloud_address
What is the output?

I have done that from both containers. In both cases they download the index.html. Connectivity between them seems to exist.

I want to be clear. When I say that the connectivity seems to exist, that is just for the wget commands. The error still shows when I try to save the settings, and the integration app still doesnt work.

Could you please send a screenshot of an error entry in the Logging app in your Nextcloud after saving the connector settings?

This is the only error I see in the nginx error log for nextcloud:

2021/10/29 11:06:57 [error] 413#413: *9535 upstream timed out (110: Operation timed out) while reading response header from upstream, client: <MY PUBLIC IP>, server: _, request: "PUT /apps/onlyoffice/ajax/settings/address HTTP/1.1", upstream: "fastcgi://", host: ""

Are there no error entries in your-nextcloud-address/index.php/settings/admin/logging ?

I see no other error entries in any log, nextcloud or onlyoffice.