What can I do?

Here is my worry. My visa expired last year 04/09/18 and the application was made on time. I did my biometric on 01/10/19 on parent route visa on my daughter . So basically it’s just a renewal plus adding I have a new twins as well.
Home office said their decision is outside their standard service time but will reply within six months. After six months and nothing was heard from them, I contacted them via my solicitor. HO responded back that they had dispatched a package since 17/01/19 and sent the tracking number. Checking the tracking number, it showed it was delivered but not delivery address or travel history of mail could be seen. Royal Mail said it looked strange as their GPS could not even tracked where it’s delivered. The solicitor’s address is the correspondence address and the solicitor’s secretary did not have any package for that day recorded.
Called back HO and they still insisted they sent a package. Royal Mail claimed nothing was delivered by them. Hence I don’t even know what the HO sent or if any decision is being made. I have written an official letter to get a response of what decision was made though.
My worry is this, will I be classed as overstayer now if what they sent in January was further proof of documents or whatsoever and I haven’t responded on time as I have never received anything from them anyway. Whose fault is it now since I haven’t received anything and yet they claimed they sent a package. Pls shed some lights on this. Thanks

If DX courier hasn't contacted you then at least you should be known that you haven't yet been issued the visa. If your solicitor was representing you then definitely the correspondence must have been sent to him.