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And I don't believe your intercept URL syntax is correct. But the solution depends on your full request URL. 
You are obviously chopping off the URL origion, so let's add `**` at the beginning, try this:
`cy.intercept('GET', '**/api/v1/oktaConfig').as('exp')`

 and I don't know if you are chopping off the end URL path, if yes then try this:
`cy.intercept('GET', '**/api/v1/oktaConfig/*').as('exp')`

And as mentioned above this should be moved before the first `cy.visit()`
```
Cypress.Commands.add('login', (username, password) => {
  cy.session([username, password], () => {
    cy.intercept('GET', '**/api/v1/oktaConfig/*').as('exp')
      cy.visit('/');
      ...
```