Apr 01, 2011 · Hi, Since upgrading to 2.3 version 1.8, whenever I try to check my credit balance or whenever I try to access the unlock panel I always get this message: Connection problem or invalid MMI code. I am PAYG with Tesco, but now the phone show O2 as the provider. Any thoughts on this will be very appr... Nov 03, 2014 · If I try to do it using MMI codes I get: "connection problem or invalid MMI code" I have chatted with support and they say they will get back to me within 48, but, twice, I have not gotten a response. Jun 09, 2015 · My tablet says "connection problem or invalid MMI code" when trying to chech balance. in Phones and Tablets. by Thobile (User) (1.1k points) asked Jun 9, 2015. 0 votes .