I doubt your agent, assuming you're not using the listing agent, can do much. The house has a weather related issue that must be addressed. You could offer to pay some of the cost to thaw the pipes and proceed with your inspection, if that's cheaper than the alternative.
You could threaten to walk on the deal if you have a legitimate escape built into your contract.
Locking a rate is always for a set time period and extending a lock costs money. You can request the seller bear that cost if you can't proceed quickly with a back-up threat to leave the transaction if they don't. There are things you can try, I just don't know if any will be successful.
Your agent should be dealing with the listing agent and demanding they do their job to get the house sold. Apart from that, I'm not sure what else you can do.