Can't get bearerToken from web application

[popandepo]

I'm trying to get a bearer token using https://oauth.developers.visma.com/service-registry/documentation/authentication#serviceApp since i have a tenantID-based system.
oauth2 works perfectly well and i can log in and get my email address, but the response when i try to get a token is 400 invalid_client.
i would like to keep both functions in one app if possible

[Yıldırım]

Hi, 

what is the status of your application ? Has it been approved in the developer portal ? 

and if you want to use client_credentials OAuth2 grant type your application type should be "Service"

Please also double-check your clientID & Secret via the application tab. 

An application can not have multiple authentication method. It can be either one

[popandepo]

it has been approved and is invite only on visma app store.
requests for vismanet employee api have been approved.

it is a web application currently, as the service doesn't have oidc
My current thoughts are to have the users log in using oidc/visma connect then i get an email address back, i can then use that valid and verified email address to look up in a database which tenantIDs are available and display information for each available employee tenant andd use the tenantid to get a token for API calls.

i assumed that would be the only way, but would it then be possible to forego all the visma app store/tenant stuff and only use oidc/appid+secret to connect to the api? how would that handle multiple tenants?
Thank you for your response!