TDS payment through income tax portal started recently and before that, maximum persons tried to pay through NSDL portal which was the only portal to make TDS payment. What you can do is as workaround that you need to download csi file for any of the past period from NSDL portal i.e. period in which they have made payment through NSDL (whether or not that period within TDS return quarter that we have taken up for filing). Use that csi file to generate fvu file. Use that fvu file to upload on income tax portal for TAN login.
Generally, if there is mismatch in challan between csi file (downloaded from NSDL since it belongs to different period) and challan as per return data, system will also generate "Electronic_Statement_Warning_File.H T M L" file containing details of such mismatch alongwith fvu file. You just need to ignore that H T M L file and no need to worry if your challan data in TDS return is correct as per actual challan (which you have paid through income tax portal).
In case if you haven't paid TDS on NSDL portal anytime in past, all you can do is to make TDS payment of Rs.1 through NSDL portal using their TAN details, and wait for 4-5 days to get that payment reflect in NSDL OLTAS records. Now, download csi file after 4-5 days and use it in the same as mentioned above.
I understand that this is an error on income tax portal and would be rectified in future but for the current filing, you can try abovementioned workaround.