Can't expand newly created Open Extension in MS Graph

TLDR version: This was caused by not encoding the Graph query string before calling Graph - not an API issue!

I've created a new Open Extension for a particular user. I can read the user, or the Open Extension specifically, but I can't use $expand to return the user with the Open Extension together in a single call.

I'm using Application authentication to AAD (with a secret), and that may or may not have something to do with it. Every example I've found uses the /v1.0/me shortcut in Graph Explorer.

EDIT: I quickly got an answer that did not take this into account. The MS Graph Explorer only allows for authentication via a user account and does not help me

I can consistently add, read and delete an extension. The only issue is expanding the extensions attributes when reading.

$uri = "https://graph.microsoft.com/v1.0/users/user@domain.com.au/extensions"

$body = '{
    "@odata.type":"microsoft.graph.openTypeExtension",
    "extensionName":"au.com.domain.customAttributes",
    "shoesize":"large"
}'

$query = Invoke-RestMethod -Method Post -Uri $uri -ContentType "application/json" -Body $body -Headers @{Authorization = "Bearer $token"} -ErrorAction Stop

#Modify an existing custom attribute
$uri = "https://graph.microsoft.com/v1.0/users/user@domain.com.au/extensions/au.com.domain.customAttributes"

$body = '{
    "shoesize":"small"
}'

$query = Invoke-RestMethod -Method Patch -Uri $uri -ContentType "application/json" -Body $body -Headers @{Authorization = "Bearer $token"} -ErrorAction Stop

## Read user without extension attributes
$uri = "https://graph.microsoft.com/v1.0/users/user@domain.com.au"
$user = Invoke-RestMethod -Method Get -Uri $uri -Headers @{Authorization = "Bearer $token"} -ErrorAction Stop
Write-Host $user

## Read extension attributes only in separate call
$uri = "https://graph.microsoft.com/v1.0/users/user@domain.com.au/extensions/au.com.domain.customAttributes"
$customAttributes = Invoke-RestMethod -Method Get -Uri $uri -Headers @{Authorization = "Bearer $token"} -ErrorAction Stop
Write-Host $customAttributes

## Delete a custom extention
$uri = "https://graph.microsoft.com/v1.0/users/user@domain.com.au/extensions/au.com.domain.customAttributes"
$customAttributes = Invoke-RestMethod -Method DELETE -Uri $uri -Headers @{Authorization = "Bearer $token"} -ErrorAction Stop

Write-Host $customAttributes

I need to be able to use a filter to get 100 users from 55000, including all of their open extension attributes.

EDIT: I suspect this may be a query parameters related problem and I think I'll sleep on this before rewriting the question maybe?

This works for example:

$uri = "https://graph.microsoft.com/v1.0/users"
$users = Invoke-RestMethod -Method Get -Uri $uri -Headers @{Authorization = "Bearer $token"}  -ContentType "application/json" -ErrorAction Stop 

This gives me the first 100 users for my tenant. Adding any query parameter at all breaks the request. I get a 400 error, even if example the same Graph call in Graph Explorer gives a meaningful response.

I'm using Invoke-RestMethod in powershell to make the calls to Graph... I suspect I need to try a different way of making calls or try passing extra parameters to Invoke-RestMethod