I have an STP dated 15/10/2018 which still shows as "pending". Others which showed the same changed from pending when I clicked on the details tab. I tried to download a full file replacement, but the portal doesn't give me the choice to go back that far to replace a file.
You've done the right thing by clicking on the Detail link as that will force GovConnect to obtain the latest status message based on the result from the ATO. If a pay event is still in 'Pending' state for an extended period of time its more than likely due to an issue with the ATO's SBR2 service at the time of submission eg, maintenance, issue, outage etc.
I also have this problem. I have a pending submission from 10/10/18. I have been back several times over the last few months and clicked on details to trying and force it to say success but have had no luck. If I go into the file it says Null against the ATO receipt number. How do I know it has definitely submitted