It is possible to check the balance of gift cards and store credit through Solutions POS and Power BI. 

Checking Balance on Solutions

While logged into the POS screen, click the More Menu

Select Balance

Select the type of balance you would like to validate

Type, swipe, or scan the number in the first field. Then, press Validate 

This will then show the balance of the store credit or gift card in the Balance field. If a customer would like a printed receipt of their balance, press the Print Detail button on the bottom right

This should also give a QR code that can be scanned as well when they'd like to use their gift card/store credit.

Checking Balance on Power BI

On Power BI, navigate to the Serial Payments Balance report.

From here, select the correct payment Method ID on the top

Using the information you have, you can look for a customer's store credit or gift card by filtering the SerialID or End Balance columns.