Aggregating rows from a condition in a linking table in SQL
A possible solution can be :
The first select gets all combination of date and error combination that exist in the tables.
If  you actually want all possible Dates, you need to add another created table, with all possiible dates


CREATE TABLE Code_SKU_Combos
    ([ErrorCode] varchar(5), [Device] varchar(2))
;
    
INSERT INTO Code_SKU_Combos
    ([ErrorCode], [Device])
VALUES
    ('12.24', 'A2'),
    ('12.25', 'A2'),
    ('12.26', 'A2'),
    ('12.24', 'B3'),
    ('12.26', 'B3'),
    ('12.25', 'C4')
;
GO




CREATE TABLE DailyUses
    ([Uses] int, [Date] Date, [Device] varchar(2))
;
    
INSERT INTO DailyUses
    ([Uses], [Date], [Device])
VALUES
    (3, '2020-3-1', 'A2'),
    (5, '2020-3-1', 'B3'),
    (1, '2020-3-2', 'A2'),
    (12, '2020-3-3', 'C4')
;
GO




SELECT DISTINCT [Date],[ErrorCode] FROM DailyUses CROSS JOIN  Code_SKU_Combos
GO


Date       | ErrorCode
:--------- | :--------
2020-03-01 | 12.24    
2020-03-01 | 12.25    
2020-03-01 | 12.26    
2020-03-02 | 12.24    
2020-03-02 | 12.25    
2020-03-02 | 12.26    
2020-03-03 | 12.24    
2020-03-03 | 12.25    
2020-03-03 | 12.26    




SELECT ISNULL (SUM([Uses]),0) AS Uses, DateComp as [Date],[errorcomp] AS ErrorCode
FROM (SELECT DISTINCT [Date] as DateComp,[ErrorCode] AS errorcomp FROM DailyUses CROSS JOIN  Code_SKU_Combos) t1
LEFT JOIN (
DailyUses d INNER JOIN Code_SKU_Combos c ON d.[Device] = c.[Device]) ON t1.DateComp = d.[Date] 
AND  t1.errorcomp = c.[ErrorCode]

GROUP BY [DateComp],[errorcomp]
ORDER BY [DateComp],[errorcomp]
GO


Uses | Date       | ErrorCode
---: | :--------- | :--------
   8 | 2020-03-01 | 12.24    
   3 | 2020-03-01 | 12.25    
   8 | 2020-03-01 | 12.26    
   1 | 2020-03-02 | 12.24    
   1 | 2020-03-02 | 12.25    
   1 | 2020-03-02 | 12.26    
   0 | 2020-03-03 | 12.24    
  12 | 2020-03-03 | 12.25    
   0 | 2020-03-03 | 12.26    


db&lt;&gt;fiddle here