CPQ Quote API, I can't save the quote - salesforce

Question

I can't save the quote.
Doing the query:
select
ApexClass.name, Id, CreatedDate, CreatedById, JobType,
ApexClassId, Status, JobItemsProcessed, TotalJobItems,
NumberOfErrors, CompletedDate, MethodName, ExtendedStatus,
ParentJobId, LastProcessed, LastProcessedOffset
from
AsyncApexJob
order by
CreatedDate desc
I get this error:
Calculation error on quote Q-13761: "UNAUTHORIZED"
Code:
public with sharing class QuoteCalculator {
public void calculate(QuoteModel quote, String callbackClass) {
system.debug('quote: ' +quote);
system.debug('callbackClass: ' +callbackClass);
QuoteCalculatorContext ctx = new QuoteCalculatorContext(quote, callbackClass);
SBQQ.ServiceRouter.load('SBQQ.QuoteAPI.QuoteCalculator', null, JSON.serialize(ctx));
system.debug('QuoteCalculator.calculate');
}
private class QuoteCalculatorContext {
private QuoteModel quote; //The quote and callbackClass properties are called
in the API code by the exact names seen here.
private String callbackClass; //Altering these property names will cause
calculator API calls to fail.
private QuoteCalculatorContext(QuoteModel quote, String callbackClass) {
this.quote = quote;
this.callbackClass = callbackClass;
}
}
}
anonymous window:
QuoteReader reader = new QuoteReader();
QuoteModel quote = reader.read('a0p1w000BhfXzAAJ');
System.debug(quote);
quote.lineItems[0].record.SBQQ__Quantity__c = 2;
QuoteCalculator calculator = new QuoteCalculator();
calculator.calculate(quote, 'MyCallback')

Answer 1

Preface
I had (almost) the same exact code base as yours, and got the same error message.
In my case there was an other sandbox I could test my code, and it turned out to be working properly there.
Cause
Later found out that the Salesforce CPQ's Calculation Quote API is using Heroku to do the calculations in order to avoid apex limits exhaustion.
From this it can be deducted, that it needs to have a Connected App. I checked the Apps -> Connected Apps setup, and found that no record was listed under the "Connected Apps OAuth Usage" page for the Salesforce CPQ. (On my other sandbox there was a "Steelbrick CPQ" row.)
From this I concluded that this might be the reason for this behaviour.
Seems like something went wrong during the "Authorize new Calculation Service" process. (Or there was a sandbox refresh and something else went wrong during it.)
Solution
The bad news is that the option to authorize a new calculation service is only visible for the first time you configure the package, which you might already done. (Well... if you haven't done, then this is a great news, because your problem is probably solved. :D) (Otherwise read further.)
The good news is I figured out a solution for the case when you already done this, yet that "Steelbrick CPQ" row is missing.
Created a scratch org and installed the Salesforce CPQ package, then before I clicked on the "Authorize new Calculation Service" link under the "Pricing and Calculation" tab in the Settings Editor, I checked the source code in hope of finding something of interest.
I did.
This link: https://rest-na.steelbrick.com/oauth/auth/https%3A%2F%2Ftest.salesforce.com/SBQQ
(⚠️NOTE: You might have to change it according to your location. There are several servers across the globe:
rest-au.steelbrick.com
rest-eu.steelbrick.com
rest-jp.steelbrick.com
rest-na.steelbrick.com
But for me the above pasted link was generated on the settings page. Which is only interesting, because I live in the EU, yet, for some reason I got the link to the rest-NA server... whatever.gif
So just make sure if you click on the link, in the address bar you can find the appropriate salesforce instance URL.)
Conclusion
With this link you won't have to reinstall the package, you just have to click on it, and allow the access from Steelbrick and the missing row will appear, and you will be authorized to use the Calculation API.