Please run pihole -d from the terminal of the Raspberry Pi and type y to allow the debug log to be uploaded. This will help us see what the current configuration is and prevent us from having to ask a lot of questions while troubleshooting your issue.
I did read a post that contained a very similar issue to the one I am experiencing and the poster had also followed the Crosstalk instruction.
If the error "no internet access with custom 127.0.0.1#5335" is the result of following the Crosstalk instructions, might one of my options be simply removing the whole of the install and starting afresh?
If the above is an option where would I find a reliable, simple, set of instructions to follow, I used the Crosstalk instructions as they were well presented on YouTube and also clearly written down.