can't claim grants on staging when using `aab` builds

Description

Originally found/reported by @stephendonner, it looks like we can’t claim grants on staging due to the following:

2021-05-16 19:22:11.331 31751-31751/? V/chromium: [<VERBOSE6:logging_util.cc>(136)] 
    [ RESPONSE - OnRequest ]
    > Url: https://grant.rewards.bravesoftware.com/v2/attestations/safetynet/90d8d547-cb56-4fd0-a31a-5f87800cacff
    > Result: Failure
    > HTTP Code: 400
    > Body: {"message":"Error verifying token: No matching APK signing certificate found","code":400}

We should also check and ensure this isn’t happening on production or we’ll run into a lot support/issues when users start receiving their ad grants.

Steps to reproduce

1. install Brave using an internal sharing link (used 1.24.83 Chromium: 90.0.4430.93)
2. change rewards to staging using the developer settings
3. once switched to staging, enable rewards and attempt to claim a grant

Actual result

Expected result

Should be able to claim/use grants on staging.

Issue reproduces how often

100% reproducible using the above STR.

Version/Channel Information:

• Can you reproduce this issue with the current Play Store version? N/A (Yes when using 1.24.x RC)
• Can you reproduce this issue with the current Play Store Beta version? Yes
• Can you reproduce this issue with the current Play Store Nightly version? Yes

Device details

• Install type (ARM, x86): ARM
• Device type (Phone, Tablet, Phablet): Samsung S10+
• Android version: Android 11

Brave version

• 1.24.83 Chromium: 90.0.4430.93 - Reproduced

Website problems only

• Does the issue resolve itself when disabling Brave Shields? N/A
• Does the issue resolve itself when disabling Brave Rewards? N/A
• Is the issue reproducible on the latest version of Chrome? N/A

Additional information

CCing @SergeyZhukovsky @anthonypkeane @bsclifton @brave/legacy_qa @evq

[kjozwiak]

Removing the release/blocking as this works when claiming grants on aab builds that were uploaded into GPS. We’ll need to figure out how to get around this re: being able to claim grants on staging on aab builds that were downloaded via internal sharing.

I have the same problem. Brave: 1.23.73 Chromium:90.0.4430.93 I made a post in the community, however, it fell into hold, saying it needs moderation, so far nothing and I can’t even comment in the community.

This is a different issue and your best bet is going through https://community.brave.com. CCing @Hollons in case he can help re: why your posts are being flagged as needing moderation.

[kjozwiak]

Labeled as release/blocking as we need to make sure this isn’t happening on production either.