This is Lana from Shopify. I see you're looking to transfer a domain into Shopify so I wanted to help you out.
You mentioned that you have already tried to do this many times, but it was not successful, so I will outline the steps for this here, and you can see if maybe you missed something here or if there is a particular step that you're stuck on.
The transfer process involves going to your domain host first (in your case, Dinsol.in) and asking them to unlock the domain for transfer. You should then receive an authorisation code from them which you will be able to use on the Shopify side of things in the Online store > Domains section when you go to Transfer domain:
You will then need to enter your domain name without any prefixes such as www. etc. When you click Next, you will see one of the following messages:
After this, you will be asked to enter the authorisation code, and you will be able to initiate the transfer.
Please do note that after you initiate the transfer, the process could take up to 20 days. That could be one reason that you're not seeing it on Shopify yet, you may need to give it more time if you have successfully completed the steps above.
For this information, you can see our help doc on Domain Transfers.
Let me know if you have any other questions on this, and I will be happy to help!