Not Printing.

Thermal printing calculators do not use ink. Instead, they require that you use thermal paper. If you attempt to use standard (not thermal) paper with one of these models, then you will not be able to print.
Thermal paper is heat-sensitive. Printing is accomplished when the print head uses a heating element to heat the paper and create the printing, rather than using an ink roll or an ink ribbon. Standard paper is not heat-sensitive, so when the print head passes over it and heats it, there is no reaction from the paper, and therefore nothing appears on the paper.
Thermal paper can be obtained from most office supply stores. Usually 2 1/4" or 58mm thermal paper is used (standard size).