I can't talk to PAM to complete my mission. I killed the courser like she asked but she's not giving me a reward and not talking to me. Is there a specific time of the day she would talk to me or is it a glitch?

She(?) should. Never had a "day of time" problem with her/it

Damn tin-can is buggy for me as well. Gave me only one of the Jackpot quests and just stopped after that. Never gave me another one no matter how many times I talked to her. Luckily, after the first one I was given access to the BW so it didn't bother me too much because that's all I wanted out of those boring quests, but I just find the Railroad to be buggy in general in regards to their side/radiant quests. Hell, I never got the Memory Interrupted quest to trigger, despite having done everything to make it trigger.

For me she's stuck in a defensive mode (to avoid spoilers) even though I haven't actually talked to the person to do the thing to put her in a defensive mode.

The only time I could ever talk to her is if drummer boy told me she needed to talk to me. Without drummer boy saying anything she wouldn't give me a quest. The quests in the railroad seemed to alternate for me. I'd go do a Randolph safe house mission, then drummer boy would give me a pam mission. Back and forth.. I wouldn't get one until I had done the other. I'd say if you aren't getting a Pam quest then go do another quest for the railroad and see if that triggers it.

According to the wikia.. if you ever blew her off by stating "maybe later" or "not interested" she could stop giving any quest updates.

When the quest "Tactical Thinking" was open, she stopped talking to me.

I'm pretty sure it's because you completed Blind Betrayal. Once Blind Betrayal is completed for the BoS, PAM will be hacked by the BoS, and you can no longer interact with her except for in order to progress the main quest line. The only solution is to become the enemy with the BoS or completing the game as the Minutemen