One has nothing to do with the other....Doing missions from other contacts won't help Martin call.
Well, that's screwed up then because I didn't use any glitch to boost up my RP, so I'm kinda punished for using in-game activities to level.
Try doing his gang attacks and spending time in free roam. I gained 5 levels really fast (grinding race wins to unlock lsc mods) and missed Lester's and Merryweather calls. I spent about 3 hours in free mode and they began to call one after the other.
I tried that too (well not intentionally) but that didn't seem to work either. I spent hours in free mode playing with my crew (having car meet ups, driving in a line to a random place,etc) but I still haven't unlocked Martin.
I have unlocked every Merryweather option. Lester, Simeon, Trevor, I can send a Mugger, etc. I did gang attacks (and received an award for doing 5 on the same day), I still do them now & then, and still no Martin.
I'm starting to think he just doesn't want to work with me.
I take it you cant even call martin to reqest jobs? Do you have survivals (shield) Gang attacks (only as you drive near to one, big red circles) showing up on your mini map? Silly questions I Know. I personally ranked up to level 60 - 70 by doing mainly missions alone, a few survivals, gang attacks, crate drops, in friends only lobbies before getting into races. (I havent got this problem). Once i started doing races a lot, I ranked up quicker & I ignored a lot of missions poping up on my phone and the good ones poping up became few and far between. Now at a high rank I join missions through quick jobs on my phone of friend sent missions inbetween messing around. So I dont get sent a lot off high end missions from contacts sent to me without me reqesting them by ringing them. Even then they still send me low end missions most of the time.
So I would suggest going to invite/friends only freeroam lobby and do every mission that gets sent to YOUR phone. Unless you know for SURE that you have already completed it WITHOUT joining a Player/friend /invite sent MISSION. There maybe a certain amount of missions or a certain mission from one of the the lower contacts that triggers martins call. This may take a couple of sessions
I have just looked for answers for this problem all over the web in different forums and no response has had a positive definate solution. In other words nobody was like ....."yey thats sorted it out"
(Tre FacTor) is right about trying gang attacks and staying in freemode to get the calls, keep doing that. Do a few missions ,steal and sell a baller for a few minites then do some more missions. Like I said before some of the low paid simeon missions are hard with no good payout but I think they unlock 1 or 2 lamar missions you can not EVER ring for.
Iam thinking outside of the box, but Ive got a feeling i might be right. good luck