[Resolved] 2 Known Problems: (un)Register site-key + Unable to Set Static Homepage

Dear WPML support,

Back again and in need of your help on known problems in the support forum but without clear fix.

Situation:
1) This problem occurs on a production server: We have redesigned our theme and did some homepage content changes. On test environment no issues so ready for go-live. We are using a deployment so we pushed changes to production. Problem: homepage redirects to 404 page and unable to set / update the static homepage in under "reading". It doesnt matter what type of page we try to set as homepage (also once for which we have 100% translations in all languages) all fail and can't be saved. Error: "Your post doesn't exist or its translation is not published in EN, FR or NL". It also only happens when WPML is activated, if all WPML plugins are disable it works without issue.

2) After deactivating and activating the plugin we got the known error about invalid site-key back. Hence tried to register it again or renew subscription. But it fails over and over, even when updating wp_options tabel with the sitekey by removing it and retrying doesnt work. It simply repopulates the datafield.

So two issues:

1) Unable to properly register WPML with the sitekey from my account
2) Unable to set a fresh new static homepage under Settings --> Reading

Links to our previous forum posts and discussions with Lauren:
https://wpml.org/forums/topic/not-able-to-revalidate-license-or-unregister-to-add-new-site-key/page/2/
https://wpml.org/forums/topic/unable-to-revalidate-license-or-unregister-to-add-new-site-key/

Links to exactly similar problems around setting the static homepage:
https://wpml.org/forums/topic/settingsreadingstatic-home-page-cannot-save-to-other-page-it-resets/
https://wpml.org/forums/topic/i-could-not-change-frontpage-after-i-activate-wpml/
https://wpml.org/forums/topic/cannot-set-a-static-page-for-frontpage/

Actions we took for 1:
- Deleting site from WPML panel, adding a new one --> site-key the same
- Adding site-key via wp-config file --> error: "You are using an invalid site key defined as the constant OTGS_INSTALLER_SITE_KEY_WPML (most likely in wp-config.php). Please remove it or use the correct value in order to be able to register correctly.
- Updating plugins manually --> no change
- Removed sitekey from wp_options tabel and saved. No change and is NULL, after activating the plugin it auto populates the field again with the same hashed value (serialized).

Actions we took for 2:
- Trying to delete existing homepages and start from scratch with an empty homepage. Not able to set
- Trying to connect pages to other translations to ensure linkage --> not able to select as homepage
- Removed (untranslated) widgets to ensure all components are translated --> no luck
- Selecting a page with all translations available via pages (we can click the pencil as link to the translation and wordpress editor recognizes the translation) --> unable to select page to set homepage
- Basically we can't set any static homepage with WPML enabled.

Please help us out.