As stated in the T&C, each user is limited to only one GCrypto account. You may be unable to register to GCrypto if your email address is already linked to an existing GCrypto account.
Please ensure that you are not sharing an email address with someone else who is registered to GCrypto. If you are sharing an email address with someone who has a GCrypto account already, please update your email address on the GCash app first and re-apply to GCrypto.