So I've been doing freelance design for this company and I work through email and my website with this one client. I have a Chrome extension that let's me track activity on an email after it has been sent. This client last read one of my emails about 10 days ago, then I send another 2 regarding changes he requested on the design. And today I sent a follow up mail and none of these have even been read. This client is really nice, I've worked with him on two other projects (aside from the current one) and also talked about the next one. Should I be worried that he hasn't replied or even read my emails? On one of the previous projects he vanished for like a week or something, and came back to tell me he was really busy and couldn't make time to answer me (which I completely understand). I'm just worried since I didn't ask for an advance for the current project and we're half-way through. I probably shouldn't worry at all and should just wait for his answer but I thought that reading some of your stories/advice would make me worry a little less.
You must try giving him a courtesy call, speaking on the phone makes a huge difference as compared to sending an email.
No client wants to leave their project in between - possibility of he ignoring you could mean that your project is no longer a priority for your client, or the client has not enough financial resources to fund this project or they have found somebody else.
The situation can only be understood after speaking with the client. You can surely stop working on the existing project until there is a reply from your client. Nobody is so busy that they cannot reply to discuss or understand the project status for which they have already paid for.
The best scenario would be that you will receive the balance amount to complete the project. Alternatively, you should be prepared to take it as a learning and move on.