Haven't recieved my rewards points for march or april

In order for support to check into your account, you'll want to post in the Xbox Rewards Questions support forum. If you're looking for VIP rebates, keep in mind that rebates are calculated after the end of the month and given by the 15th of the next month
so it would be too soon to see credits pending for April. Also, supscriptions, in-game consumables, preorders, and any purchases that went towards any other offers on the site do not count towards your rebate.

Hello Kelesis Azel,

You cannot receive both payback and offer completion for a purchase, as stated in our FAQ:

What type of Rewards can I earn?

In addition to our special events and offers, there are two easy ways to earn Rewards Credits each month; by completing missions or special offers, or with a MyVIP Star Rank. To see current
missions, visit the MyMissions page. For more details, please see the Terms and Conditions. Don't forget to check back often to see what's new, as missions are updated frequently!

To learn more about your MyVIP Star Rank, which gives you a percentage back on what you buy in the Xbox Store, visit the MyRewards page. Once you have earned at least 1 Star, you'll start earning each month
based on your qualifying purchases from the previous month.

Please note: Xbox Live Rewards members may not earn Rewards Credits for multiple offers based on performing the same action. For example, your purchases made to complete a monthly mission won't also be eligible for MyVIP.

Since you chose to opt in to the Simply Rewarding offer last month, you did not receive payback for those March purchases. They went towards the Simply Rewarding offer. Regarding your April purchases, also from our FAQ:

When will my MyVIP Rewards Credits be deposited into my Microsoft account?

The total Rewards earned will be calculated at the end of each month. Typically you'll receive your MyVIP earnings in your account by the 15th of the following month, though this is subject to the program's current deposit
terms. Be sure to keep an eye on MyStatement on the
MyRewards page to track your progress and watch your Rewards Credits total grow!

We have not yet calculated the month's MyVIP, so it is too early to see the Credits pending. However, your MyVIP progress is accurate.

VIP Rewards will take longer as the VIP Rewards over March will appear 15th of April.

Hello,

From the FAQ on Vault Credits:

I claimed Rewards Credits from the vault. When will I receive them?

If you claim Rewards Credits from the MyVIP Vault, they should appear as pending in your account within 96 hours. Once they are pending in your account, the normal deposit process kicks in. Generally if you have over 5,000 Rewards Credits pending in your
account in the first half of any given month, that amount will be converted to your local currency and deposited into your Microsoft account on or around the 30th of that same month. If the Credits show as pending in the second half of the month, that amount
will be deposited into your Microsoft account on or around the 15th of the next month.

Please note you need at least 5,000 Rewards Credits pending to automatically trigger a deposit, though you can request a deposit for the next scheduled date as long as you have 1,000 Credits pending. Also, if you have ongoing issues with us depositing
into your account, such as your account not matching up with your billing location, you might want to consider choosing a different prize from the vault, as we won’t be able to deliver your Rewards Credits until the deposit issue is resolved.

Furthermore, Xbox Live Rewards Credits and MS Reward points are not the same currency.

96 hours is how long it takes for them to be added as pending on the Rewards site. They would be scheduled to deposit into your Microsoft account balance around June 15.