Salam
put the bike registration number in the mtmis database
https://mtmis.excise.punjab.gov.pk/
you will see following details,
1) Owner details (name of current owner on registration book/card)
2) Last payment details (tokens paid/any other payments such as transfer fee payment)
3) Vehicle details (make, variant color etc)
4) Vehicle application tracking
the 4th part is useful for you in this case since you will be able to see if an application for transfer of ownership already exists in the system or not and whether the challan has been paid for it or not (in this case it is highly likely that it has been paid)
As the message says, an application for transfer already has been filed for the vehicle. This basically means that someone made a transfer application against the bike registration number and paid the challan. That application is most probably at stage of "biometric verification".
This message specifically is there because the "challan fee" has been paid when the application was generated using the app.
Get in touch with the seller and ask if he tried to sell the bike to someone else before he sold it to you and was there initiation of a transfer of ownership application?
The transfer of ownership application is always initiated by the buyer using either epay or the go punjab app. Initially you put in the registration number then put in your NIC and proceed to where you want the vehicle inspection to be done (closest excise office) and then you generate a challan and pay it via banking app and then you go for biometric verification and inspection before the ownership is transferred in your name.
The only way to get out of this is to go to the excise office with all documents of the bike (registration card and file along with buyers receipt and seller's NIC copy) and file an application for removal of this application from their system.