Nighthawk M6 Pro (MR 6450) SIM problem

My recently purchased Nighthawk M6 Pro works fine with 2 SIM cards from 2 different operators in Czech Republic - O2 and Vodafone. I just purchased a new data only SIM card from Vodafone, that does not work. When inserted, the modem shows a searching message. The SIM card works fine when inserted to my mobile phone. Any suggestions please?