There is a missing line before var1=... var1 = ((var1 * var1 * (BME280_S64_t)calibrationData.P3) >> 8) + ((var1 * (BME280_S64_t)calibrationData.P2) << 12); (See datasheet.)
There is a missing line before var1=...
var1 = ((var1 * var1 * (BME280_S64_t)calibrationData.P3) >> 8) + ((var1 * (BME280_S64_t)calibrationData.P2) << 12);
(See datasheet.)