Blocking in robots.txt urls which are also being redirected means the redirection will never be found.

Don't use robots to block duplicate content!

Often webpages are accessible by a number of different URLs (this is often true in content management systems like Drupal). The temptation is to block the unwanted URLs so that they are not crawled by Google.

In fact, the best way to handle multiple URLs is to use a 301 redirect and/or the canonical META tag.

Don't combine robots and 301s

Most commonly, people realise that Google is crawling webpages it shouldn't, so they block those pages using robots.txt and set up a 301 redirect to the correct pages hoping to kill two birds with one stone (i.e. remove unwanted urls from the index and pass PageRank juice to the correct pages). However, Google will not follow a 301 redirect on a page blocked with robots.txt.

This leads to a situation where the blocked pages hang around indefinitely because Google isn't able to follow the 301 redirect.

Update your robots.txt files:

On the source site, remove all robots.txt directives. This allows Googlebot to discover all redirects to the new site and update our index.
On the destination site, make sure the robots.txt file allows all crawling. This includes crawling of images, CSS, JavaScript, and other page assets, apart from the URLs you are certain you do not want crawled.

Allow default subdomain indexing (by search engines) :
This feature allows search engines to index the default subdomain. If a 301 redirect is set up, the default subdomain and the connected domain will be merged together. We advise you to enable this feature.