I created a notebook instance using the following as a reference.

https://cloud.google.com/blog/ja/topics/developers-practitioners/pytorch-google-cloud-how-train-pytorch-models-ai-platform

gcloud-------vvmlbaainnmmaooccneo--ccoccsttiihateetwemmit-llaobaanideelroggeoirrlkoee-nsaa-=k--t=kttgdspfyu-ooperapssrrufiome-i---anji=czctduselneeoyrltcy1n=rpitat=-t1eevn=psr0-=ecdyta0cNreetaloVseon1\uI\prd-nDclcaatIrehr=Aea-d\1_ar1-Ttn-4\Eei7Sn-\LegcAx-u_ap1Tml14pa0lt-\efn-ooirtnmes-btroaeonlkceseas\\e\

At that time, I was unable to create the notebook instance due to the following error.

ERROR:(gcloud.notebooks.instances.create)Thezone'projects/{project}/zones/us-central1-a'doesnothaveenoughresourcesavailabletofulfilltherequest.(resourcetype:compute)'.

Therefore, I changed the location from us-central1-a to us-central1-b, and was able to create the instance.

gcloud-------vvmlbaainnmmaooccneo--ccoccsttiihateetwemmit-llaobaanideelroggeoirrlkoee-nsaa-=k--t=kttgdspfyu-ooperapssrrufiome-i---anji=czctduselneeoyrltcy1n=rpitat=-t1eevn=psr0-=ecdyta0cNreetaloVseon1\uI\prd-nDclcabtIrehr=Aea-d\1_ar1-Ttn-4\Eei7Sn-\LegcAx-u_ap1Tml14pa0lt-\efn-ooirtnmes-btroaeonlkceseas\\e\

I hope this helps others facing the same issue.