I ran the pic through ai and it suggested this, like hydraulic cement?
https://dampstore.ie/product/hydradry-waterstop-membrane-5kg/?srsltid=AfmBOorEP1rcOq7ewFGuYjVZ04NNlr3ZYNlFEBtiwY5r7DwJKfMvAiCn
Looking for the light blue / grey product that is sealing between the yellow down wall and the tar/bitumen roof (no idea what its called)
Job was done few years ago and the black stuff came in blocks and the guys came with big containers and gas bottles and melted and poured it on the roof...