For Years I've Been Taking Furosemide 40 Mg From One

For years I've been taking Furosemide 40 mg from one mfg and it works great. just recently received a mail order of Furosemide 40 mg from a different mfg. taken 3 days and my body is not reacting the same as before - seems to be not working. is this possible or could there be something else wrong?