Invalid Amount Sent

I had the same issue and in Memberpress settings I went unchecked
Memberpress Settings | General | Disable Rewrite Rules

This seemed to work for me.

Still not working after unchecked the Rewrite Rules.

Have you tried changing the currency type ?

Currently, I use the Naira. My user may not be able to use any other currency.

process_create_subscription:
MeprTransaction Object
(
[object_type:MeprBaseMetaModel:private] => transaction
[meta_table:MeprBaseMetaModel:private] => transaction_meta
[rec:protected] => stdClass Object
(
[id] => 47
[amount] => 1500.00
[total] => 1500.00
[tax_amount] => 0.00
[tax_rate] => 0.000
[tax_desc] =>
[tax_class] => standard
[user_id] => 0
[product_id] => 757
[coupon_id] => 0
[trans_num] => mp-txn-6015698483950
[status] => pending
[txn_type] => payment
[gateway] => qnkxq9-2nz
[prorated] => 0
[created_at] => 2021-01-30 14:13:26
[expires_at] => 2021-04-30 23:59:59
[subscription_id] => 19
[corporate_account_id] => 0
[parent_transaction_id] => 0
[tax_compound] => 0
[tax_shipping] => 1
[response] =>
)

[attrs:protected] => Array
(
[0] => id
[1] => amount
[2] => total
[3] => tax_amount
[4] => tax_rate
[5] => tax_desc
[6] => tax_class
[7] => user_id
[8] => product_id
[9] => coupon_id
[10] => trans_num
[11] => status
[12] => txn_type
[13] => gateway
[14] => prorated
[15] => created_at
[16] => expires_at
[17] => subscription_id
[18] => corporate_account_id
[19] => parent_transaction_id
)

[defaults:protected] =>
)

Just shared the debug message