Installed Subscription Proxy blocks the user from non-US regions on navigating to any site

[ValentinaPC]

Affected versions:

• All Firefox;

Affected FxA versions:

• 1.175.0;

Affected Platforms:

• Windows 10 (64-bit);

Preconditions

• Have the latest Subscription Proxy (that points to FxA stage) installed;
• use a Firefox profile with non-US region set (use Windscribe)

Steps to reproduce

1. Sign in to SP.
2. Try to turn it on.
3. Navigate to addons.mozilla.com (or other site).

Expected result:

• The user is able to navigate to any site without restrictions.

Actual result:

• The user is blocked from navigating to other sites.

Notes:

• The offline message is also displayed for a few seconds in US regions.
  

Video for the overall issue:

[ValentinaPC]

Note: reproducing only while using Mozilla/SV account.

LE - While using the latest signed version of the Subscription Proxy, on stage (179.0.2), FX 78 and WIn 10 x64 we also:

• reproduced the issue while using a "mailinator" account
• [intermittent] reproduced the issue while having a US region set.

Adding a video for clarity.

Rising severity to "major".